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Original file line number | Diff line number | Diff line change |
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--- | ||
id: candy | ||
title: Candy | ||
sidebar_label: 0135 Candy | ||
tags: | ||
- Greedy | ||
- LeetCode | ||
- Java | ||
- Python | ||
- C++ | ||
description: "This is a solution to the Candy problem on LeetCode." | ||
--- | ||
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## Problem Description | ||
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There are n children standing in a line. Each child is assigned a rating value given in the integer array ratings. | ||
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You are giving candies to these children subjected to the following requirements: | ||
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- Each child must have at least one candy. | ||
- Children with a higher rating get more candies than their neighbors. | ||
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Return the minimum number of candies you need to have to distribute the candies to the children. | ||
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### Examples | ||
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**Example 1:** | ||
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``` | ||
Input: ratings = [1,0,2] | ||
Output: 5 | ||
Explanation: You can allocate to the first, second and third child with 2, 1, 2 candies respectively. | ||
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``` | ||
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**Example 2:** | ||
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Input: ratings = [1,2,2] | ||
Output: 4 | ||
Explanation: You can allocate to the first, second and third child with 1, 2, 1 candies respectively. | ||
The third child gets 1 candy because it satisfies the above two conditions. | ||
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``` | ||
Input: root = [1,2,2,null,3,null,3] | ||
Output: false | ||
``` | ||
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### Constraints | ||
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- n == ratings.length | ||
- 1 <= n <= 2 * 10^4 | ||
- 0 <= ratings[i] <= 2 * 10^4 | ||
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--- | ||
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## Solution for Candy Distribution Problem | ||
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### Intuition And Approach | ||
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To solve this problem, we can use a greedy approach. We can start by assigning each child 1 candy. Then, we iterate over the ratings array twice, once from left to right and once from right to left, adjusting the number of candies as needed to satisfy the given conditions. | ||
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#### Code in Different Languages | ||
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<Tabs> | ||
<TabItem value="Java" label="Java"> | ||
<SolutionAuthor name="@YourName"/> | ||
```java | ||
public class Solution { | ||
public int candy(int[] ratings) { | ||
int n = ratings.length; | ||
int[] candies = new int[n]; | ||
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// Initialize all candies to 1 | ||
for (int i = 0; i < n; i++) { | ||
candies[i] = 1; | ||
} | ||
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// Left to right pass | ||
for (int i = 1; i < n; i++) { | ||
if (ratings[i] > ratings[i - 1]) { | ||
candies[i] = candies[i - 1] + 1; | ||
} | ||
} | ||
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// Right to left pass | ||
for (int i = n - 2; i >= 0; i--) { | ||
if (ratings[i] > ratings[i + 1] && candies[i] <= candies[i + 1]) { | ||
candies[i] = candies[i + 1] + 1; | ||
} | ||
} | ||
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int totalCandies = 0; | ||
for (int candy : candies) { | ||
totalCandies += candy; | ||
} | ||
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return totalCandies; | ||
} | ||
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public static void main(String[] args) { | ||
Solution solution = new Solution(); | ||
int[] ratings1 = {1, 0, 2}; | ||
int[] ratings2 = {1, 2, 2}; | ||
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System.out.println(solution.candy(ratings1)); // Output: 5 | ||
System.out.println(solution.candy(ratings2)); // Output: 4 | ||
} | ||
} | ||
``` | ||
</TabItem> | ||
<TabItem value="Python" label="Python"> | ||
<SolutionAuthor name="@YourName"/> | ||
```python | ||
class Solution(object): | ||
def candy(self, ratings): | ||
""" | ||
:type ratings: List[int] | ||
:rtype: int | ||
""" | ||
n = len(ratings) | ||
candies = [1] * n | ||
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# Left to right pass | ||
for i in range(1, n): | ||
if ratings[i] > ratings[i - 1]: | ||
candies[i] = candies[i - 1] + 1 | ||
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# Right to left pass | ||
for i in range(n - 2, -1, -1): | ||
if ratings[i] > ratings[i + 1]: | ||
candies[i] = max(candies[i], candies[i + 1] + 1) | ||
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return sum(candies) | ||
``` | ||
</TabItem> | ||
<TabItem value="C++" label="C++"> | ||
<SolutionAuthor name="@mahek0620"/> | ||
```cpp | ||
#include <vector> | ||
#include <algorithm> | ||
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using namespace std; | ||
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class Solution { | ||
public: | ||
int candy(vector<int>& ratings) { | ||
int n = ratings.size(); | ||
vector<int> candies(n, 1); | ||
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// Left to right pass | ||
for (int i = 1; i < n; i++) { | ||
if (ratings[i] > ratings[i - 1]) { | ||
candies[i] = candies[i - 1] + 1; | ||
} | ||
} | ||
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// Right to left pass | ||
for (int i = n - 2; i >= 0; i--) { | ||
if (ratings[i] > ratings[i + 1]) { | ||
candies[i] = max(candies[i], candies[i + 1] + 1); | ||
} | ||
} | ||
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// Sum up all candies | ||
int totalCandies = 0; | ||
for (int candy : candies) { | ||
totalCandies += candy; | ||
} | ||
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return totalCandies; | ||
} | ||
}; | ||
``` | ||
</TabItem> | ||
</Tabs> | ||
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#### Complexity Analysis | ||
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- Time Complexity: O(n) where n is the number of children (length of the ratings array). | ||
ajay-dhangar marked this conversation as resolved.
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- Space Complexity: O(n) for storing the candies array. | ||
mahek0620 marked this conversation as resolved.
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</tabItem> | ||
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## References | ||
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- **LeetCode Problem:** [Candy Problem](https://leetcode.com/problems/candy/) | ||
- **Solution Link:** [Candy Solution on LeetCode](https://leetcode.com/problems/candy/solutions/5273312/candy-solution) | ||
- **Authors GeeksforGeeks Profile:** [Mahek Patel](https://leetcode.com/u/mahekrpatel611/) | ||
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--- |
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