|
| 1 | +--- |
| 2 | +id: squares-of-a-sorted-array |
| 3 | +title: Squares of a sorted array |
| 4 | +sidebar_label: 977. Squares of a Sorted Array |
| 5 | + |
| 6 | +tags: |
| 7 | +- Array |
| 8 | +- Vector |
| 9 | + |
| 10 | +description: "This is a solution to the squares of a sorted array problem on LeetCode." |
| 11 | +--- |
| 12 | + |
| 13 | +## Problem Description |
| 14 | +Given an integer array `nums` sorted in **non-decreasing** order, return an array of ***the squares of each number*** *sorted in non-decreasing order.* |
| 15 | + |
| 16 | +### Examples |
| 17 | + |
| 18 | +**Example 1:** |
| 19 | +``` |
| 20 | +Input: nums = [-4,-1,0,3,10] |
| 21 | +Output: [0,1,9,16,100] |
| 22 | +Explanation: After squaring, the array becomes [16,1,0,9,100]. |
| 23 | +After sorting, it becomes [0,1,9,16,100]. |
| 24 | +``` |
| 25 | + |
| 26 | +**Example 2:** |
| 27 | +``` |
| 28 | +Input: nums = [-7,-3,2,3,11] |
| 29 | +Output: [4,9,9,49,121] |
| 30 | +
|
| 31 | +``` |
| 32 | + |
| 33 | + |
| 34 | +### Constraints |
| 35 | +- `1 <= nums.length <= 10^4` |
| 36 | +- `-10^4 <= nums[i] <= 10^4` |
| 37 | +- `nums` is sorted in **non-decreasing** order. |
| 38 | + |
| 39 | +**Follow up:** Squaring each element and sorting the new array is very trivial, could you find an `O(n)` solution using a different approach? |
| 40 | + |
| 41 | + |
| 42 | +## Solution for Sqaures of a Sorted Array |
| 43 | +### Approach |
| 44 | +#### Brute Force |
| 45 | +- **Square Each Element**: Iterate through the array and square each element. |
| 46 | + |
| 47 | +- **Sort the Resulting Array**: Sort the array of squares. |
| 48 | + |
| 49 | +**Implementation:** |
| 50 | +```python |
| 51 | +def sortedSquares(nums): |
| 52 | + # Step 1: Square each element |
| 53 | + squared_nums = [num ** 2 for num in nums] |
| 54 | + |
| 55 | + # Step 2: Sort the array of squares |
| 56 | + squared_nums.sort() |
| 57 | + |
| 58 | + return squared_nums |
| 59 | + |
| 60 | +# Example usage |
| 61 | +nums = [-4, -1, 0, 3, 10] |
| 62 | +print(sortedSquares(nums)) # Output: [0, 1, 9, 16, 100] |
| 63 | +``` |
| 64 | + |
| 65 | +**Complexity:** |
| 66 | +- Time Complexity: `O(nlogn)` due to the sorting step, where `n` is the number of elements in `nums`. |
| 67 | +- Space Complexity: `O(n)` for storing the sqaured numbers. |
| 68 | + |
| 69 | +**Corner Cases:** |
| 70 | +- Empty array: Should return an empty array. |
| 71 | +- All non-negative or all non-positive numbers: Should still work correctly without special handling. |
| 72 | + |
| 73 | +#### Optimized Approach |
| 74 | +- **Two-pointer Technique**: Utilize two pointers, one at the beginning (`left`) and one at the end (`right`) of the array. |
| 75 | +- **Compare and Insert**: Compare the absolute values of the elements pointed by `left` and `right`. Insert the square of the larger absolute value at the end of the result array and move the corresponding pointer inward. |
| 76 | +- **Continue Until Pointers Meet**: Repeat the comparison and insertion until the pointers meet. |
| 77 | + |
| 78 | +**Implementation:** |
| 79 | + |
| 80 | +```python |
| 81 | +def sortedSquares(nums): |
| 82 | + n = nums.length |
| 83 | + result = [0] * n |
| 84 | + left, right = 0, n - 1 |
| 85 | + position = n - 1 |
| 86 | + |
| 87 | + while left <= right: |
| 88 | + if abs(nums[left]) > abs(nums[right]): |
| 89 | + result[position] = nums[left] ** 2 |
| 90 | + left += 1 |
| 91 | + else: |
| 92 | + result[position] = nums[right] ** 2 |
| 93 | + right -= 1 |
| 94 | + position -= 1 |
| 95 | + |
| 96 | + return result |
| 97 | + |
| 98 | +# Example usage |
| 99 | +nums = [-4, -1, 0, 3, 10] |
| 100 | +print(sortedSquares(nums)) # Output: [0, 1, 9, 16, 100] |
| 101 | + |
| 102 | +``` |
| 103 | + |
| 104 | +**Complexity:** |
| 105 | +- Time Complexity: `O(n)` because we are traversing the array only once with the two-pointer technique. |
| 106 | +- Space Complexity: `O(n)` for the result array. |
| 107 | + |
| 108 | +**Corner Cases:** |
| 109 | +- Empty array: Should return an empty array. |
| 110 | +- All non-negative or all non-positive numbers: Handled naturally by the two-pointer technique without special cases. |
| 111 | +- Array with single element: Both approaches handle this case correctly. |
| 112 | + |
| 113 | + |
| 114 | +<Tabs> |
| 115 | + <TabItem value="Solution" label="Solution"> |
| 116 | + |
| 117 | +#### Implementation |
| 118 | + |
| 119 | + ```jsx live |
| 120 | + function Solution(arr) { |
| 121 | + var sortedSquares = function(nums) { |
| 122 | + const result = new Array(nums.length) |
| 123 | + let i = nums.length - 1 |
| 124 | + let j = 0 |
| 125 | + let k = nums.length - 1 |
| 126 | + |
| 127 | + while (i >= 0) { |
| 128 | + if (Math.abs(nums[j]) > Math.abs(nums[k])) { |
| 129 | + result[i] = nums[j] * nums[j]; |
| 130 | + ++j; |
| 131 | + } else { |
| 132 | + result[i] = nums[k] * nums[k]; |
| 133 | + --k; |
| 134 | + } |
| 135 | + --i; |
| 136 | + } |
| 137 | + return result |
| 138 | + }; |
| 139 | + const input = [-4,-1,0,3,10] |
| 140 | + const originalInput = [...input] |
| 141 | + const output = sortedSquares(input) |
| 142 | + return ( |
| 143 | + <div> |
| 144 | + <p> |
| 145 | + <b>Input: </b> |
| 146 | + {JSON.stringify(originalInput)} |
| 147 | + </p> |
| 148 | + <p> |
| 149 | + <b>Output:</b> {output.toString()} |
| 150 | + </p> |
| 151 | + </div> |
| 152 | + ); |
| 153 | + } |
| 154 | + ``` |
| 155 | + |
| 156 | +#### Complexity Analysis |
| 157 | + |
| 158 | + - Time Complexity: $O(n)$ |
| 159 | + - Space Complexity: $O(n)$ |
| 160 | + |
| 161 | + ## Code in Different Languages |
| 162 | + |
| 163 | + <Tabs> |
| 164 | + |
| 165 | + <TabItem value="JavaScript" label="JavaScript"> |
| 166 | + <SolutionAuthor name="@vansh-codes" /> |
| 167 | + |
| 168 | + ```javascript |
| 169 | + var sortedSquares = function(nums) { |
| 170 | + const result = new Array(nums.length) |
| 171 | + let i = nums.length - 1 |
| 172 | + let j = 0 |
| 173 | + let k = nums.length - 1 |
| 174 | + |
| 175 | + while (i >= 0) { |
| 176 | + if (Math.abs(nums[j]) > Math.abs(nums[k])) { |
| 177 | + result[i] = nums[j] * nums[j]; |
| 178 | + j++; |
| 179 | + } else { |
| 180 | + result[i] = nums[k] * nums[k]; |
| 181 | + k--; |
| 182 | + } |
| 183 | + i--; |
| 184 | + } |
| 185 | + return result; |
| 186 | + }; |
| 187 | + ``` |
| 188 | + |
| 189 | + </TabItem> |
| 190 | + |
| 191 | + <TabItem value="TypeScript" label="TypeScript"> |
| 192 | + <SolutionAuthor name="@vansh-codes" /> |
| 193 | + |
| 194 | + ```typescript |
| 195 | + function sortedSquares(nums: number[]): number[] { |
| 196 | + const result = new Array(nums.length); |
| 197 | + let i = nums.length - 1; |
| 198 | + let j = 0; |
| 199 | + let k = nums.length - 1; |
| 200 | + |
| 201 | + while (i >= 0) { |
| 202 | + if (Math.abs(nums[j]) > Math.abs(nums[k])) { |
| 203 | + result[i] = nums[j] * nums[j]; |
| 204 | + j++; |
| 205 | + } else { |
| 206 | + result[i] = nums[k] * nums[k]; |
| 207 | + k--; |
| 208 | + } |
| 209 | + i--; |
| 210 | + } |
| 211 | + |
| 212 | + return result; |
| 213 | + } |
| 214 | + ``` |
| 215 | + |
| 216 | + </TabItem> |
| 217 | + |
| 218 | + <TabItem value="Python" label="Python"> |
| 219 | + <SolutionAuthor name="@vansh-codes" /> |
| 220 | + |
| 221 | + ```python |
| 222 | +
|
| 223 | + class Solution(object): |
| 224 | + def sortedSquares(self, nums): |
| 225 | + result = [0] * len(nums) |
| 226 | + i = len(nums) - 1 |
| 227 | + j = 0 |
| 228 | + k = len(nums) - 1 |
| 229 | + |
| 230 | + while i >= 0: |
| 231 | + if abs(nums[j]) > abs(nums[k]): |
| 232 | + result[i] = nums[j] ** 2 |
| 233 | + j += 1 |
| 234 | + else: |
| 235 | + result[i] = nums[k] ** 2 |
| 236 | + k -= 1 |
| 237 | + i -= 1 |
| 238 | + |
| 239 | + return result |
| 240 | +
|
| 241 | + ``` |
| 242 | + |
| 243 | + </TabItem> |
| 244 | + |
| 245 | + <TabItem value="Java" label="Java"> |
| 246 | + <SolutionAuthor name="@vansh-codes" /> |
| 247 | + |
| 248 | + ```java |
| 249 | + import java.util.Arrays; |
| 250 | +
|
| 251 | + class Solution { |
| 252 | + public int[] sortedSquares(int[] nums) { |
| 253 | + int[] result = new int[nums.length]; |
| 254 | + int i = nums.length - 1; |
| 255 | + int j = 0; |
| 256 | + int k = nums.length - 1; |
| 257 | + |
| 258 | + while (i >= 0) { |
| 259 | + if (Math.abs(nums[j]) > Math.abs(nums[k])) { |
| 260 | + result[i] = nums[j] * nums[j]; |
| 261 | + j++; |
| 262 | + } else { |
| 263 | + result[i] = nums[k] * nums[k]; |
| 264 | + k--; |
| 265 | + } |
| 266 | + i--; |
| 267 | + } |
| 268 | + |
| 269 | + return result; |
| 270 | + } |
| 271 | + } |
| 272 | + ``` |
| 273 | + |
| 274 | + </TabItem> |
| 275 | + |
| 276 | + <TabItem value="C++" label="C++"> |
| 277 | + <SolutionAuthor name="@vansh-codes" /> |
| 278 | + |
| 279 | + ```cpp |
| 280 | + class Solution { |
| 281 | + public: |
| 282 | + int sortedSquares(vector<int>& nums) { |
| 283 | + vector<int> result(nums.size()); |
| 284 | + int i = nums.size()-1, j = 0, k = nums.size()-1; |
| 285 | + while(i >= 0) |
| 286 | + { |
| 287 | + if(abs(nums[j]) > abs(nums[k])) |
| 288 | + { |
| 289 | + result[i] = nums[j] * nums[j]; |
| 290 | + ++j; |
| 291 | + } |
| 292 | + else |
| 293 | + { |
| 294 | + result[i] = nums[k] * nums[k]; |
| 295 | + --k; |
| 296 | + } |
| 297 | + --i; |
| 298 | + } |
| 299 | + return result; |
| 300 | + } |
| 301 | + }; |
| 302 | +
|
| 303 | + ``` |
| 304 | + |
| 305 | +</TabItem> |
| 306 | +</Tabs> |
| 307 | + |
| 308 | +</TabItem> |
| 309 | +</Tabs> |
| 310 | + |
| 311 | +## References |
| 312 | + |
| 313 | +- **LeetCode Problem**: [Squares of a Sorted Array](https://leetcode.com/problems/squares-of-a-sorted-array/description) |
| 314 | + |
| 315 | +- **Solution Link**: [LeetCode Solution](https://leetcode.com/problems/squares-of-a-sorted-array/solutions/) |
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