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‎README.md

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| <!-- --> | <!-- --> | <!-- --> | <!-- --> | <!-- --> | <!-- -->
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| 0046 |[Permutations](src/main/js/g0001_0100/s0046_permutations)| Medium | Top_100_Liked_Questions, Top_Interview_Questions, Array, Backtracking, Big_O_Time_O(n\*n!)_Space_O(n+n!) | 0 | 100.00
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#### Day 12 Dynamic Programming
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| <!-- --> | <!-- --> | <!-- --> | <!-- --> | <!-- --> | <!-- -->
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| 0039 |[Combination Sum](src/main/js/g0001_0100/s0039_combination_sum)| Medium | Top_100_Liked_Questions, Array, Backtracking, Big_O_Time_O(2^n)_Space_O(n+2^n) | 1 | 98.51
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#### Day 11 Recursion Backtracking
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| <!-- --> | <!-- --> | <!-- --> | <!-- --> | <!-- --> | <!-- -->
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| 0055 |[Jump Game](src/main/js/g0001_0100/s0055_jump_game)| Medium | Top_100_Liked_Questions, Top_Interview_Questions, Array, Dynamic_Programming, Greedy, Big_O_Time_O(n)_Space_O(1) | 0 | 100.00
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164167
#### Day 13 Dynamic Programming
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| <!-- --> | <!-- --> | <!-- --> | <!-- --> | <!-- --> | <!-- -->
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| 0045 |[Jump Game II](src/main/js/g0001_0100/s0045_jump_game_ii)| Medium | Top_100_Liked_Questions, Array, Dynamic_Programming, Greedy, Big_O_Time_O(n)_Space_O(1) | 0 | 100.00
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#### Day 14 Dynamic Programming
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| 0055 |[Jump Game](src/main/js/g0001_0100/s0055_jump_game)| Medium | Top_100_Liked_Questions, Top_Interview_Questions, Array, Dynamic_Programming, Greedy, Big_O_Time_O(n)_Space_O(1) | 0 | 100.00
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| 0045 |[Jump Game II](src/main/js/g0001_0100/s0045_jump_game_ii)| Medium | Top_100_Liked_Questions, Array, Dynamic_Programming, Greedy, Big_O_Time_O(n)_Space_O(1) | 0 | 100.00
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#### Day 5
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401407
| <!-- --> | <!-- --> | <!-- --> | <!-- --> | <!-- --> | <!-- -->
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| 0053 |[Maximum Subarray](src/main/js/g0001_0100/s0053_maximum_subarray)| Medium | Top_100_Liked_Questions, Top_Interview_Questions, Array, Dynamic_Programming, Divide_and_Conquer, Big_O_Time_O(n)_Space_O(1) | 1 | 85.69
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#### Day 6
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| <!-- --> | <!-- --> | <!-- --> | <!-- --> | <!-- --> | <!-- -->
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|-|-|-|-|-|-
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| 0042 |[Trapping Rain Water](src/main/js/g0001_0100/s0042_trapping_rain_water)| Hard | Top_100_Liked_Questions, Top_Interview_Questions, Array, Dynamic_Programming, Two_Pointers, Stack, Monotonic_Stack, Big_O_Time_O(n)_Space_O(1) | 0 | 100.00
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#### Day 10
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| <!-- --> | <!-- --> | <!-- --> | <!-- --> | <!-- --> | <!-- -->
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| 0048 |[Rotate Image](src/main/js/g0001_0100/s0048_rotate_image)| Medium | Top_100_Liked_Questions, Top_Interview_Questions, Array, Math, Matrix, Big_O_Time_O(n^2)_Space_O(1) | 0 | 100.00
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#### Day 8
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| <!-- --> | <!-- --> | <!-- --> | <!-- --> | <!-- --> | <!-- -->
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|-|-|-|-|-|-
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| 0049 |[Group Anagrams](src/main/js/g0001_0100/s0049_group_anagrams)| Medium | Top_100_Liked_Questions, Top_Interview_Questions, Array, String, Hash_Table, Sorting, Big_O_Time_O(n\*k_log_k)_Space_O(n) | 24 | 91.62
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#### Day 12
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| <!-- --> | <!-- --> | <!-- --> | <!-- --> | <!-- --> | <!-- -->
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| 0039 |[Combination Sum](src/main/js/g0001_0100/s0039_combination_sum)| Medium | Top_100_Liked_Questions, Array, Backtracking, Big_O_Time_O(2^n)_Space_O(n+2^n) | 1 | 98.51
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| 0046 |[Permutations](src/main/js/g0001_0100/s0046_permutations)| Medium | Top_100_Liked_Questions, Top_Interview_Questions, Array, Backtracking, Big_O_Time_O(n\*n!)_Space_O(n+n!) | 0 | 100.00
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### Udemy
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| 0003 |[Longest Substring Without Repeating Characters](src/main/js/g0001_0100/s0003_longest_substring_without_repeating_characters)| Medium | Top_100_Liked_Questions, Top_Interview_Questions, String, Hash_Table, Sliding_Window, Big_O_Time_O(n)_Space_O(1), AI_can_be_used_to_solve_the_task | 3 | 98.96
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| 0020 |[Valid Parentheses](src/main/js/g0001_0100/s0020_valid_parentheses)| Easy | Top_100_Liked_Questions, Top_Interview_Questions, String, Stack, Big_O_Time_O(n)_Space_O(n) | 0 | 100.00
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| 0005 |[Longest Palindromic Substring](src/main/js/g0001_0100/s0005_longest_palindromic_substring)| Medium | Top_100_Liked_Questions, Top_Interview_Questions, String, Dynamic_Programming, Big_O_Time_O(n)_Space_O(n) | 10 | 99.54
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| 0049 |[Group Anagrams](src/main/js/g0001_0100/s0049_group_anagrams)| Medium | Top_100_Liked_Questions, Top_Interview_Questions, Array, String, Hash_Table, Sorting, Big_O_Time_O(n\*k_log_k)_Space_O(n) | 24 | 91.62
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#### Udemy Binary Search
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| <!-- --> | <!-- --> | <!-- --> | <!-- --> | <!-- --> | <!-- -->
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| 0001 |[Two Sum](src/main/js/g0001_0100/s0001_two_sum)| Easy | Top_100_Liked_Questions, Top_Interview_Questions, Array, Hash_Table, Big_O_Time_O(n)_Space_O(n), AI_can_be_used_to_solve_the_task | 1 | 89.15
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| 0055 |[Jump Game](src/main/js/g0001_0100/s0055_jump_game)| Medium | Top_100_Liked_Questions, Top_Interview_Questions, Array, Dynamic_Programming, Greedy, Big_O_Time_O(n)_Space_O(1) | 0 | 100.00
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| 0041 |[First Missing Positive](src/main/js/g0001_0100/s0041_first_missing_positive)| Hard | Top_100_Liked_Questions, Top_Interview_Questions, Array, Hash_Table, Big_O_Time_O(n)_Space_O(n) | 1 | 98.86
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#### Udemy Two Pointers
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| <!-- --> | <!-- --> | <!-- --> | <!-- --> | <!-- --> | <!-- -->
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| 0042 |[Trapping Rain Water](src/main/js/g0001_0100/s0042_trapping_rain_water)| Hard | Top_100_Liked_Questions, Top_Interview_Questions, Array, Dynamic_Programming, Two_Pointers, Stack, Monotonic_Stack, Big_O_Time_O(n)_Space_O(1) | 0 | 100.00
9911007
| 0015 |[3Sum](src/main/js/g0001_0100/s0015_3sum)| Medium | Top_100_Liked_Questions, Top_Interview_Questions, Array, Sorting, Two_Pointers, Big_O_Time_O(n\*log(n))_Space_O(n^2) | 31 | 91.92
9921008

9931009
#### Udemy Famous Algorithm
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| <!-- --> | <!-- --> | <!-- --> | <!-- --> | <!-- --> | <!-- -->
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| 0053 |[Maximum Subarray](src/main/js/g0001_0100/s0053_maximum_subarray)| Medium | Top_100_Liked_Questions, Top_Interview_Questions, Array, Dynamic_Programming, Divide_and_Conquer, Big_O_Time_O(n)_Space_O(1) | 1 | 85.69
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#### Udemy Sorting Algorithms
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| 0048 |[Rotate Image](src/main/js/g0001_0100/s0048_rotate_image)| Medium | Top_100_Liked_Questions, Top_Interview_Questions, Array, Math, Matrix, Big_O_Time_O(n^2)_Space_O(1) | 0 | 100.00
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#### Udemy Linked List
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| 0022 |[Generate Parentheses](src/main/js/g0001_0100/s0022_generate_parentheses)| Medium | Top_100_Liked_Questions, Top_Interview_Questions, String, Dynamic_Programming, Backtracking, Big_O_Time_O(2^n)_Space_O(n) | 0 | 100.00
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| 0039 |[Combination Sum](src/main/js/g0001_0100/s0039_combination_sum)| Medium | Top_100_Liked_Questions, Array, Backtracking, Big_O_Time_O(2^n)_Space_O(n+2^n) | 1 | 98.51
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| 0017 |[Letter Combinations of a Phone Number](src/main/js/g0001_0100/s0017_letter_combinations_of_a_phone_number)| Medium | Top_100_Liked_Questions, Top_Interview_Questions, String, Hash_Table, Backtracking, Big_O_Time_O(4^n)_Space_O(n) | 0 | 100.00
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| 0046 |[Permutations](src/main/js/g0001_0100/s0046_permutations)| Medium | Top_100_Liked_Questions, Top_Interview_Questions, Array, Backtracking, Big_O_Time_O(n\*n!)_Space_O(n+n!) | 0 | 100.00
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| 0053 |[Maximum Subarray](src/main/js/g0001_0100/s0053_maximum_subarray)| Medium | Top_100_Liked_Questions, Top_Interview_Questions, Array, Dynamic_Programming, Divide_and_Conquer, Big_O_Time_O(n)_Space_O(1) | 1 | 85.69
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| 0048 |[Rotate Image](src/main/js/g0001_0100/s0048_rotate_image)| Medium | Top_100_Liked_Questions, Top_Interview_Questions, Array, Math, Matrix, Big_O_Time_O(n^2)_Space_O(1) | 0 | 100.00
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| 0049 |[Group Anagrams](src/main/js/g0001_0100/s0049_group_anagrams)| Medium | Top_100_Liked_Questions, Top_Interview_Questions, Array, String, Hash_Table, Sorting, Big_O_Time_O(n\*k_log_k)_Space_O(n) | 24 | 91.62
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| # | Title | Difficulty | Tag | Time, ms | Time, %
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|------|----------------|-------------|-------------|----------|--------
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| 0055 |[Jump Game](src/main/js/g0001_0100/s0055_jump_game)| Medium | Top_100_Liked_Questions, Top_Interview_Questions, Array, Dynamic_Programming, Greedy, Algorithm_II_Day_12_Dynamic_Programming, Dynamic_Programming_I_Day_4, Udemy_Arrays, Big_O_Time_O(n)_Space_O(1) | 0 | 100.00
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| 0053 |[Maximum Subarray](src/main/js/g0001_0100/s0053_maximum_subarray)| Medium | Top_100_Liked_Questions, Top_Interview_Questions, Array, Dynamic_Programming, Divide_and_Conquer, Data_Structure_I_Day_1_Array, Dynamic_Programming_I_Day_5, Udemy_Famous_Algorithm, Big_O_Time_O(n)_Space_O(1) | 1 | 85.69
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| 0051 |[N-Queens](src/main/js/g0001_0100/s0051_n_queens)| Hard | Top_100_Liked_Questions, Array, Backtracking, Big_O_Time_O(N!)_Space_O(N) | 6 | 96.66
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| 0049 |[Group Anagrams](src/main/js/g0001_0100/s0049_group_anagrams)| Medium | Top_100_Liked_Questions, Top_Interview_Questions, Array, String, Hash_Table, Sorting, Data_Structure_II_Day_8_String, Programming_Skills_II_Day_11, Udemy_Strings, Big_O_Time_O(n\*k_log_k)_Space_O(n) | 24 | 91.62
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| 0048 |[Rotate Image](src/main/js/g0001_0100/s0048_rotate_image)| Medium | Top_100_Liked_Questions, Top_Interview_Questions, Array, Math, Matrix, Data_Structure_II_Day_3_Array, Programming_Skills_II_Day_7, Udemy_2D_Arrays/Matrix, Big_O_Time_O(n^2)_Space_O(1) | 0 | 100.00
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| 0046 |[Permutations](src/main/js/g0001_0100/s0046_permutations)| Medium | Top_100_Liked_Questions, Top_Interview_Questions, Array, Backtracking, Algorithm_I_Day_11_Recursion_Backtracking, Level_2_Day_20_Brute_Force/Backtracking, Udemy_Backtracking/Recursion, Big_O_Time_O(n\*n!)_Space_O(n+n!) | 0 | 100.00
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| 0045 |[Jump Game II](src/main/js/g0001_0100/s0045_jump_game_ii)| Medium | Top_100_Liked_Questions, Array, Dynamic_Programming, Greedy, Algorithm_II_Day_13_Dynamic_Programming, Dynamic_Programming_I_Day_4, Big_O_Time_O(n)_Space_O(1) | 0 | 100.00
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| 0042 |[Trapping Rain Water](src/main/js/g0001_0100/s0042_trapping_rain_water)| Hard | Top_100_Liked_Questions, Top_Interview_Questions, Array, Dynamic_Programming, Two_Pointers, Stack, Monotonic_Stack, Dynamic_Programming_I_Day_9, Udemy_Two_Pointers, Big_O_Time_O(n)_Space_O(1) | 0 | 100.00
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| 0041 |[First Missing Positive](src/main/js/g0001_0100/s0041_first_missing_positive)| Hard | Top_100_Liked_Questions, Top_Interview_Questions, Array, Hash_Table, Udemy_Arrays, Big_O_Time_O(n)_Space_O(n) | 1 | 98.86
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| 0039 |[Combination Sum](src/main/js/g0001_0100/s0039_combination_sum)| Medium | Top_100_Liked_Questions, Array, Backtracking, Algorithm_II_Day_10_Recursion_Backtracking, Level_2_Day_20_Brute_Force/Backtracking, Udemy_Backtracking/Recursion, Big_O_Time_O(2^n)_Space_O(n+2^n) | 1 | 98.51
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| 0035 |[Search Insert Position](src/main/js/g0001_0100/s0035_search_insert_position)| Easy | Top_100_Liked_Questions, Array, Binary_Search, Algorithm_I_Day_1_Binary_Search, Binary_Search_I_Day_2, Big_O_Time_O(log_n)_Space_O(1) | 0 | 100.00
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| 0034 |[Find First and Last Position of Element in Sorted Array](src/main/js/g0001_0100/s0034_find_first_and_last_position_of_element_in_sorted_array)| Medium | Top_100_Liked_Questions, Top_Interview_Questions, Array, Binary_Search, Algorithm_II_Day_1_Binary_Search, Binary_Search_I_Day_5, Big_O_Time_O(log_n)_Space_O(1) | 0 | 100.00
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| 0033 |[Search in Rotated Sorted Array](src/main/js/g0001_0100/s0033_search_in_rotated_sorted_array)| Medium | Top_100_Liked_Questions, Top_Interview_Questions, Array, Binary_Search, Algorithm_II_Day_1_Binary_Search, Binary_Search_I_Day_11, Level_2_Day_8_Binary_Search, Udemy_Binary_Search, Big_O_Time_O(log_n)_Space_O(1) | 0 | 100.00

‎src/main/js/g0001_0100/s0039_combination_sum/readme.md

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[![](https://img.shields.io/github/stars/LeetCode-in-JavaScript/LeetCode-in-JavaScript?label=Stars&style=flat-square)](https://github.com/LeetCode-in-JavaScript/LeetCode-in-JavaScript)
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[![](https://img.shields.io/github/forks/LeetCode-in-JavaScript/LeetCode-in-JavaScript?label=Fork%20me%20on%20GitHub%20&style=flat-square)](https://github.com/LeetCode-in-JavaScript/LeetCode-in-JavaScript/fork)
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## 39\. Combination Sum
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Medium
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Given an array of **distinct** integers `candidates` and a target integer `target`, return _a list of all **unique combinations** of_ `candidates` _where the chosen numbers sum to_ `target`_._ You may return the combinations in **any order**.
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The **same** number may be chosen from `candidates` an **unlimited number of times**. Two combinations are unique if the frequency of at least one of the chosen numbers is different.
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It is **guaranteed** that the number of unique combinations that sum up to `target` is less than `150` combinations for the given input.
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**Example 1:**
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**Input:** candidates = [2,3,6,7], target = 7
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**Output:** [[2,2,3],[7]]
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**Explanation:**
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2 and 3 are candidates, and 2 + 2 + 3 = 7. Note that 2 can be used multiple times.
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7 is a candidate, and 7 = 7.
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These are the only two combinations.
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**Example 2:**
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**Input:** candidates = [2,3,5], target = 8
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**Output:** [[2,2,2,2],[2,3,3],[3,5]]
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**Example 3:**
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**Input:** candidates = [2], target = 1
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**Output:** []
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**Constraints:**
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* `1 <= candidates.length <= 30`
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* `1 <= candidates[i] <= 200`
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* All elements of `candidates` are **distinct**.
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* `1 <= target <= 500`
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## Solution
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```javascript
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/**
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* @param {number[]} candidates
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* @param {number} target
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* @return {number[][]}
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*/
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var combinationSum = function(candidates, target) {
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const ans = []
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const subList = []
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const combinationSumRec = (n, candidates, target, subList, ans) => {
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if (target === 0 || n === 0) {
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if (target === 0) {
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ans.push([...subList]) // Create a copy of subList
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}
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return
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}
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if (target - candidates[n - 1] >= 0) {
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subList.push(candidates[n - 1])
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combinationSumRec(n, candidates, target - candidates[n - 1], subList, ans)
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subList.pop() // Backtracking step
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}
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combinationSumRec(n - 1, candidates, target, subList, ans)
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}
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combinationSumRec(candidates.length, candidates, target, subList, ans)
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return ans
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};
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export { combinationSum }
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```

‎src/main/js/g0001_0100/s0041_first_missing_positive/readme.md

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[![](https://img.shields.io/github/stars/LeetCode-in-JavaScript/LeetCode-in-JavaScript?label=Stars&style=flat-square)](https://github.com/LeetCode-in-JavaScript/LeetCode-in-JavaScript)
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[![](https://img.shields.io/github/forks/LeetCode-in-JavaScript/LeetCode-in-JavaScript?label=Fork%20me%20on%20GitHub%20&style=flat-square)](https://github.com/LeetCode-in-JavaScript/LeetCode-in-JavaScript/fork)
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## 41\. First Missing Positive
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Hard
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Given an unsorted integer array `nums`, return the smallest missing positive integer.
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You must implement an algorithm that runs in `O(n)` time and uses constant extra space.
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**Example 1:**
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**Input:** nums = [1,2,0]
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**Output:** 3
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**Explanation:** The numbers in the range [1,2] are all in the array.
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**Example 2:**
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**Input:** nums = [3,4,-1,1]
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**Output:** 2
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**Explanation:** 1 is in the array but 2 is missing.
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**Example 3:**
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**Input:** nums = [7,8,9,11,12]
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**Output:** 1
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**Explanation:** The smallest positive integer 1 is missing.
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**Constraints:**
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* <code>1 <= nums.length <= 10<sup>5</sup></code>
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* <code>-2<sup>31</sup> <= nums[i] <= 2<sup>31</sup> - 1</code>
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## Solution
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```javascript
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/**
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* @param {number[]} nums
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* @return {number}
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*/
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var firstMissingPositive = function(nums) {
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for (let i = 0; i < nums.length; i++) {
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while (
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nums[i] > 0 &&
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nums[i] <= nums.length &&
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nums[nums[i] - 1] !== nums[i]
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) {
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// Swap nums[i] with nums[nums[i] - 1]
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let temp = nums[nums[i] - 1]
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nums[nums[i] - 1] = nums[i]
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nums[i] = temp
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}
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}
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for (let i = 0; i < nums.length; i++) {
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if (nums[i] !== i + 1) {
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return i + 1
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}
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}
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return nums.length + 1
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};
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export { firstMissingPositive }
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```

‎src/main/js/g0001_0100/s0042_trapping_rain_water/readme.md

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[![](https://img.shields.io/github/stars/LeetCode-in-JavaScript/LeetCode-in-JavaScript?label=Stars&style=flat-square)](https://github.com/LeetCode-in-JavaScript/LeetCode-in-JavaScript)
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[![](https://img.shields.io/github/forks/LeetCode-in-JavaScript/LeetCode-in-JavaScript?label=Fork%20me%20on%20GitHub%20&style=flat-square)](https://github.com/LeetCode-in-JavaScript/LeetCode-in-JavaScript/fork)
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## 42\. Trapping Rain Water
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Hard
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Given `n` non-negative integers representing an elevation map where the width of each bar is `1`, compute how much water it can trap after raining.
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**Example 1:**
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![](https://assets.leetcode.com/uploads/2018/10/22/rainwatertrap.png)
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**Input:** height = [0,1,0,2,1,0,1,3,2,1,2,1]
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**Output:** 6
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**Explanation:** The above elevation map (black section) is represented by array [0,1,0,2,1,0,1,3,2,1,2,1]. In this case, 6 units of rain water (blue section) are being trapped.
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**Example 2:**
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**Input:** height = [4,2,0,3,2,5]
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**Output:** 9
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**Constraints:**
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* `n == height.length`
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* <code>1 <= n <= 2 * 10<sup>4</sup></code>
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* <code>0 <= height[i] <= 10<sup>5</sup></code>
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## Solution
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```javascript
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/**
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* @param {number[]} height
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* @return {number}
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*/
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var trap = function(height) {
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let l = 0
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let r = height.length - 1
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let res = 0
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let lowerWall = 0
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while (l < r) {
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let lVal = height[l]
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let rVal = height[r]
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// Determine the lower wall
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if (lVal < rVal) {
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// Update the lower wall based on the left pointer
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lowerWall = Math.max(lVal, lowerWall)
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// Add water trapped at the current position
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res += lowerWall - lVal
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// Move the left pointer
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l++
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} else {
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// Update the lower wall based on the right pointer
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lowerWall = Math.max(rVal, lowerWall)
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// Add water trapped at the current position
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res += lowerWall - rVal
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// Move the right pointer
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r--
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}
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}
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return res
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};
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export { trap }
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```

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