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| 1 | +# 977. Squares of a Sorted Array - LeetCode Solution |
| 2 | +LeetCode problem link: [977. Squares of a Sorted Array](https://leetcode.com/problems/squares-of-a-sorted-array) |
| 3 | + |
| 4 | +## LeetCode problem description |
| 5 | +Given an integer array `nums` sorted in **non-decreasing** order, return _an array of **the squares of each number** sorted in non-decreasing order._ |
| 6 | + |
| 7 | +### Example 1 |
| 8 | +```ruby |
| 9 | +Input: nums = [-4,-1,0,3,10] |
| 10 | +Output: [0,1,9,16,100] |
| 11 | +Explanation: After squaring, the array becomes [16,1,0,9,100]. |
| 12 | +After sorting, it becomes [0,1,9,16,100]. |
| 13 | +``` |
| 14 | + |
| 15 | +### Example 2 |
| 16 | +```ruby |
| 17 | +Input: nums = [-7,-3,2,3,11] |
| 18 | +Output: [4,9,9,49,121] |
| 19 | +``` |
| 20 | + |
| 21 | +### Constraints |
| 22 | +- `1 <= nums.length <= 10000` |
| 23 | +- `10000 <= nums[i] <= 10000` |
| 24 | +- `nums` is sorted in **non-decreasing** order. |
| 25 | + |
| 26 | +**Follow up**: Squaring each element and sorting the new array is very trivial, could you find an `O(n)` solution using a different approach? |
| 27 | + |
| 28 | +## Intuition behind the Solution |
| 29 | +### Solution 1: using `sort()` |
| 30 | +* Square each number in the array. |
| 31 | +* Sort the new array. |
| 32 | + |
| 33 | +### Solution 2: not using `sort()` (important) |
| 34 | +* The smallest number in the array is located inside the array, and you need to traverse to find it. |
| 35 | +* But if you think in reverse and give priority to the certain ones, the program will become simple. |
| 36 | +* The largest number in the array is located at the two ends. So, deal with the largest number first. |
| 37 | + |
| 38 | +## Complexity |
| 39 | +### Solution 1: using `sort()` |
| 40 | +* Time: `O(n * log n)`. |
| 41 | +* Space: `O(n)`. |
| 42 | + |
| 43 | +### Solution 2: not using `sort()` |
| 44 | +* Time: `O(n)`. |
| 45 | +* Space: `O(n)`. |
| 46 | + |
| 47 | +## Java |
| 48 | +### Solution 1: using `sort()` |
| 49 | +```java |
| 50 | +class Solution { |
| 51 | + public int[] sortedSquares(int[] nums) { |
| 52 | + for (var i = 0; i < nums.length; i++) { |
| 53 | + nums[i] *= nums[i]; |
| 54 | + } |
| 55 | + |
| 56 | + Arrays.sort(nums); |
| 57 | + |
| 58 | + return nums; |
| 59 | + } |
| 60 | +} |
| 61 | +``` |
| 62 | + |
| 63 | +### Solution 2: not using `sort()` |
| 64 | +```java |
| 65 | +class Solution { |
| 66 | + public int[] sortedSquares(int[] nums) { |
| 67 | + var results = new int[nums.length]; |
| 68 | + var left = 0; |
| 69 | + var right = nums.length - 1; |
| 70 | + var index = right; |
| 71 | + |
| 72 | + while (left <= right) { |
| 73 | + if (Math.abs(nums[left]) <= nums[right]) { |
| 74 | + results[index] = nums[right] * nums[right]; |
| 75 | + right -= 1; |
| 76 | + } else { |
| 77 | + results[index] = nums[left] * nums[left]; |
| 78 | + left += 1; |
| 79 | + } |
| 80 | + |
| 81 | + index -= 1; |
| 82 | + } |
| 83 | + |
| 84 | + return results; |
| 85 | + } |
| 86 | +} |
| 87 | +``` |
| 88 | + |
| 89 | +## Python |
| 90 | +### Solution 1: using `sort()` |
| 91 | +```python |
| 92 | +class Solution: |
| 93 | + def sortedSquares(self, nums: List[int]) -> List[int]: |
| 94 | + results = [num ** 2 for num in nums] |
| 95 | + |
| 96 | + results.sort() |
| 97 | + |
| 98 | + return results |
| 99 | +``` |
| 100 | + |
| 101 | +### Solution 2: not using `sort()` |
| 102 | +```python |
| 103 | +class Solution: |
| 104 | + def sortedSquares(self, nums: List[int]) -> List[int]: |
| 105 | + results = [None] * len(nums) |
| 106 | + left = 0 |
| 107 | + right = index = len(nums) - 1 |
| 108 | + |
| 109 | + while left <= right: |
| 110 | + if abs(nums[left]) <= nums[right]: |
| 111 | + results[index] = nums[right] ** 2 |
| 112 | + right -= 1 |
| 113 | + else: |
| 114 | + results[index] = nums[left] ** 2 |
| 115 | + left += 1 |
| 116 | + |
| 117 | + index -= 1 |
| 118 | + |
| 119 | + return results |
| 120 | +``` |
| 121 | + |
| 122 | +## C++ |
| 123 | +### Solution 1: using `sort()` |
| 124 | +```cpp |
| 125 | +class Solution { |
| 126 | +public: |
| 127 | + vector<int> sortedSquares(vector<int>& nums) { |
| 128 | + for (auto i = 0; i < nums.size(); i++) { |
| 129 | + nums[i] *= nums[i]; |
| 130 | + } |
| 131 | + |
| 132 | + sort(nums.begin(), nums.end()); |
| 133 | + |
| 134 | + return nums; |
| 135 | + } |
| 136 | +}; |
| 137 | +``` |
| 138 | + |
| 139 | +### Solution 2: not using `sort()` |
| 140 | +```cpp |
| 141 | +class Solution { |
| 142 | +public: |
| 143 | + vector<int> sortedSquares(vector<int>& nums) { |
| 144 | + auto results = vector<int>(nums.size()); |
| 145 | + auto left = 0; |
| 146 | + int right = nums.size() - 1; // Should not use 'auto' here because 'auto' will make this variable become `unsigned long` which has no `-1`. |
| 147 | + auto index = right; |
| 148 | + |
| 149 | + while (left <= right) { |
| 150 | + if (abs(nums[left]) <= nums[right]) { |
| 151 | + results[index] = nums[right] * nums[right]; |
| 152 | + right -= 1; |
| 153 | + } else { |
| 154 | + results[index] = nums[left] * nums[left]; |
| 155 | + left += 1; |
| 156 | + } |
| 157 | + |
| 158 | + index -= 1; |
| 159 | + } |
| 160 | + |
| 161 | + return results; |
| 162 | + } |
| 163 | +}; |
| 164 | +``` |
| 165 | + |
| 166 | +## JavaScript |
| 167 | +### Solution 1: using `sort()` |
| 168 | +```javascript |
| 169 | +var sortedSquares = function (nums) { |
| 170 | + return _.sortBy( |
| 171 | + nums.map((num) => num * num) |
| 172 | + ) |
| 173 | +}; |
| 174 | +``` |
| 175 | + |
| 176 | +### Solution 2: not using `sort()` |
| 177 | +```javascript |
| 178 | +var sortedSquares = function (nums) { |
| 179 | + const results = Array(nums.length).fill(0) |
| 180 | + let left = 0 |
| 181 | + let right = nums.length - 1 |
| 182 | + let index = right |
| 183 | + |
| 184 | + while (left <= right) { |
| 185 | + if (Math.abs(nums[left]) <= nums[right]) { |
| 186 | + results[index] = nums[right] * nums[right] |
| 187 | + right -= 1 |
| 188 | + } else { |
| 189 | + results[index] = nums[left] * nums[left] |
| 190 | + left += 1 |
| 191 | + } |
| 192 | + |
| 193 | + index -= 1 |
| 194 | + } |
| 195 | + |
| 196 | + return results |
| 197 | +}; |
| 198 | +``` |
| 199 | + |
| 200 | +## C# |
| 201 | +### Solution 1: using `sort()` |
| 202 | +```c# |
| 203 | +public class Solution { |
| 204 | + public int[] SortedSquares(int[] nums) { |
| 205 | + for (int i = 0; i < nums.Length; i++) { |
| 206 | + nums[i] *= nums[i]; |
| 207 | + } |
| 208 | + |
| 209 | + Array.Sort(nums); |
| 210 | + |
| 211 | + return nums; |
| 212 | + } |
| 213 | +} |
| 214 | +``` |
| 215 | + |
| 216 | +### Solution 2: not using `sort()` |
| 217 | +```c# |
| 218 | +public class Solution { |
| 219 | + public int[] SortedSquares(int[] nums) { |
| 220 | + var results = new int[nums.Length]; |
| 221 | + int left = 0; |
| 222 | + int right = nums.Length - 1; |
| 223 | + int index = right; |
| 224 | + |
| 225 | + while (left <= right) |
| 226 | + { |
| 227 | + if (Math.Abs(nums[left]) <= nums[right]) |
| 228 | + { |
| 229 | + results[index] = nums[right] * nums[right]; |
| 230 | + right -= 1; |
| 231 | + } |
| 232 | + else |
| 233 | + { |
| 234 | + results[index] = nums[left] * nums[left]; |
| 235 | + left += 1; |
| 236 | + } |
| 237 | + |
| 238 | + index -= 1; |
| 239 | + } |
| 240 | + |
| 241 | + return results; |
| 242 | + } |
| 243 | +} |
| 244 | +``` |
| 245 | + |
| 246 | +## Go |
| 247 | +### Solution 1: using `sort()` |
| 248 | +```go |
| 249 | +func sortedSquares(nums []int) []int { |
| 250 | + for i, _ := range nums { |
| 251 | + nums[i] *= nums[i] |
| 252 | + } |
| 253 | + |
| 254 | + sort.Sort(sort.IntSlice(nums)) |
| 255 | + |
| 256 | + return nums |
| 257 | +} |
| 258 | +``` |
| 259 | + |
| 260 | +### Solution 2: not using `sort()` |
| 261 | +```go |
| 262 | +func sortedSquares(nums []int) []int { |
| 263 | + results := make([]int, len(nums)) |
| 264 | + left := 0 |
| 265 | + right := len(nums) - 1 |
| 266 | + index := right |
| 267 | + |
| 268 | + for left <= right { |
| 269 | + if math.Abs(float64(nums[left])) <= float64(nums[right]) { |
| 270 | + results[index] = nums[right] * nums[right] |
| 271 | + right -= 1 |
| 272 | + } else { |
| 273 | + results[index] = nums[left] * nums[left] |
| 274 | + left += 1 |
| 275 | + } |
| 276 | + |
| 277 | + index -= 1 |
| 278 | + } |
| 279 | + |
| 280 | + return results |
| 281 | +} |
| 282 | +``` |
| 283 | + |
| 284 | +## Ruby |
| 285 | +### Solution 1: using `sort()` |
| 286 | +```ruby |
| 287 | +def sorted_squares(nums) |
| 288 | + nums.map { |num| num ** 2 }.sort |
| 289 | +end |
| 290 | +``` |
| 291 | + |
| 292 | +### Solution 2: not using `sort()` |
| 293 | +```ruby |
| 294 | +def sorted_squares(nums) |
| 295 | + results = Array.new(nums.length) |
| 296 | + left = 0 |
| 297 | + right = nums.size - 1 |
| 298 | + index = right |
| 299 | + |
| 300 | + while left <= right |
| 301 | + if nums[left].abs <= nums[right] |
| 302 | + results[index] = nums[right] * nums[right] |
| 303 | + right -= 1 |
| 304 | + else |
| 305 | + results[index] = nums[left] * nums[left] |
| 306 | + left += 1 |
| 307 | + end |
| 308 | + |
| 309 | + index -= 1 |
| 310 | + end |
| 311 | + |
| 312 | + results |
| 313 | +end |
| 314 | +``` |
| 315 | + |
| 316 | +## C |
| 317 | +```c |
| 318 | +// Welcome to create a PR to complete the code of this language, thanks! |
| 319 | +``` |
| 320 | + |
| 321 | +## Kotlin |
| 322 | +```kotlin |
| 323 | +// Welcome to create a PR to complete the code of this language, thanks! |
| 324 | +``` |
| 325 | + |
| 326 | +## Swift |
| 327 | +```swift |
| 328 | +// Welcome to create a PR to complete the code of this language, thanks! |
| 329 | +``` |
| 330 | + |
| 331 | +## Rust |
| 332 | +```rust |
| 333 | +// Welcome to create a PR to complete the code of this language, thanks! |
| 334 | +``` |
| 335 | + |
| 336 | +## Other languages |
| 337 | +``` |
| 338 | +// Welcome to create a PR to complete the code of this language, thanks! |
| 339 | +``` |
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