|
| 1 | +--- |
| 2 | +id: Sort-Array-By-Parity |
| 3 | +title: Sort Array By Parity |
| 4 | +sidebar_label: Sort Array By Parity |
| 5 | +tags: |
| 6 | + - Arrays |
| 7 | + - Sorting |
| 8 | +--- |
| 9 | + |
| 10 | +## Problem Description |
| 11 | + |
| 12 | +| Problem Statement | Solution Link | LeetCode Profile | |
| 13 | +| :------------------------------------------------------ | :------------------------------------------------------------------------- | :------------------------------------------------------ | |
| 14 | +| [Sort Array By Parity](https://leetcode.com/problems/sort-array-by-parity/description/) | [Sort Array By Parity Solution on LeetCode](https://leetcode.com/problems/sort-array-by-parity/solutions/) | [Nikita Saini](https://leetcode.com/u/Saini_Nikita/) | |
| 15 | + |
| 16 | +## Problem Description |
| 17 | + |
| 18 | +Given an integer array `nums`, move all the even integers at the beginning of the array followed by all the odd integers. |
| 19 | + |
| 20 | +Return any array that satisfies this condition. |
| 21 | + |
| 22 | +### Example 1: |
| 23 | + |
| 24 | +**Input:** `nums = [3, 1, 2, 4]` |
| 25 | +**Output:** `[2, 4, 3, 1]` |
| 26 | +**Explanation:** The outputs `[4, 2, 3, 1]`, `[2, 4, 1, 3]`, and `[4, 2, 1, 3]` would also be accepted. |
| 27 | + |
| 28 | +### Example 2: |
| 29 | + |
| 30 | +**Input:** `nums = [0]` |
| 31 | +**Output:** `[0]` |
| 32 | + |
| 33 | +## Constraints |
| 34 | + |
| 35 | +- `1 <= nums.length <= 5000` |
| 36 | +- `0 <= nums[i] <= 5000` |
| 37 | + |
| 38 | +## Approach |
| 39 | + |
| 40 | +1. **Identify even and odd integers**: Iterate through the array and separate the even and odd integers. |
| 41 | +2. **Rearrange the array**: Place all even integers at the beginning of the array followed by the odd integers. |
| 42 | + |
| 43 | +## Solution |
| 44 | + |
| 45 | +### Python |
| 46 | + |
| 47 | +```python |
| 48 | +def sortArrayByParity(nums): |
| 49 | + even = [x for x in nums if x % 2 == 0] |
| 50 | + odd = [x for x in nums if x % 2 != 0] |
| 51 | + return even + odd |
| 52 | + |
| 53 | +# Example usage |
| 54 | +nums = [3, 1, 2, 4] |
| 55 | +print(sortArrayByParity(nums)) # Output: [2, 4, 3, 1] |
| 56 | +``` |
| 57 | + |
| 58 | +### Java |
| 59 | + |
| 60 | +```java |
| 61 | +import java.util.*; |
| 62 | + |
| 63 | +public class EvenOddArray { |
| 64 | + public static int[] sortArrayByParity(int[] nums) { |
| 65 | + List<Integer> even = new ArrayList<>(); |
| 66 | + List<Integer> odd = new ArrayList<>(); |
| 67 | + |
| 68 | + for (int num : nums) { |
| 69 | + if (num % 2 == 0) { |
| 70 | + even.add(num); |
| 71 | + } else { |
| 72 | + odd.add(num); |
| 73 | + } |
| 74 | + } |
| 75 | + |
| 76 | + even.addAll(odd); |
| 77 | + return even.stream().mapToInt(i -> i).toArray(); |
| 78 | + } |
| 79 | + |
| 80 | + public static void main(String[] args) { |
| 81 | + int[] nums = {3, 1, 2, 4}; |
| 82 | + System.out.println(Arrays.toString(sortArrayByParity(nums))); // Output: [2, 4, 3, 1] |
| 83 | + } |
| 84 | +} |
| 85 | +``` |
| 86 | + |
| 87 | +### C++ |
| 88 | + |
| 89 | +```cpp |
| 90 | +#include <vector> |
| 91 | +#include <iostream> |
| 92 | + |
| 93 | +std::vector<int> sortArrayByParity(std::vector<int>& nums) { |
| 94 | + std::vector<int> even, odd; |
| 95 | + for (int num : nums) { |
| 96 | + if (num % 2 == 0) { |
| 97 | + even.push_back(num); |
| 98 | + } else { |
| 99 | + odd.push_back(num); |
| 100 | + } |
| 101 | + } |
| 102 | + even.insert(even.end(), odd.begin(), odd.end()); |
| 103 | + return even; |
| 104 | +} |
| 105 | + |
| 106 | +int main() { |
| 107 | + std::vector<int> nums = {3, 1, 2, 4}; |
| 108 | + std::vector<int> result = sortArrayByParity(nums); |
| 109 | + for (int num : result) { |
| 110 | + std::cout << num << " "; |
| 111 | + } |
| 112 | + // Output: 2 4 3 1 |
| 113 | +} |
| 114 | +``` |
| 115 | +
|
| 116 | +### C |
| 117 | +
|
| 118 | +```c |
| 119 | +#include <stdio.h> |
| 120 | +#include <stdlib.h> |
| 121 | +
|
| 122 | +void sortArrayByParity(int* nums, int numsSize, int* returnSize) { |
| 123 | + int* result = (int*)malloc(numsSize * sizeof(int)); |
| 124 | + int evenIndex = 0, oddIndex = numsSize - 1; |
| 125 | + |
| 126 | + for (int i = 0; i < numsSize; ++i) { |
| 127 | + if (nums[i] % 2 == 0) { |
| 128 | + result[evenIndex++] = nums[i]; |
| 129 | + } else { |
| 130 | + result[oddIndex--] = nums[i]; |
| 131 | + } |
| 132 | + } |
| 133 | + *returnSize = numsSize; |
| 134 | + for (int i = 0; i < numsSize; ++i) { |
| 135 | + nums[i] = result[i]; |
| 136 | + } |
| 137 | + free(result); |
| 138 | +} |
| 139 | +
|
| 140 | +int main() { |
| 141 | + int nums[] = {3, 1, 2, 4}; |
| 142 | + int numsSize = sizeof(nums) / sizeof(nums[0]); |
| 143 | + int returnSize; |
| 144 | + sortArrayByParity(nums, numsSize, &returnSize); |
| 145 | + |
| 146 | + for (int i = 0; i < numsSize; ++i) { |
| 147 | + printf("%d ", nums[i]); |
| 148 | + } |
| 149 | + // Output: 2 4 3 1 |
| 150 | + return 0; |
| 151 | +} |
| 152 | +``` |
| 153 | + |
| 154 | +### JavaScript |
| 155 | + |
| 156 | +```javascript |
| 157 | +function sortArrayByParity(nums) { |
| 158 | + let even = []; |
| 159 | + let odd = []; |
| 160 | + |
| 161 | + for (let num of nums) { |
| 162 | + if (num % 2 === 0) { |
| 163 | + even.push(num); |
| 164 | + } else { |
| 165 | + odd.push(num); |
| 166 | + } |
| 167 | + } |
| 168 | + |
| 169 | + return [...even, ...odd]; |
| 170 | +} |
| 171 | + |
| 172 | +// Example usage |
| 173 | +let nums = [3, 1, 2, 4]; |
| 174 | +console.log(sortArrayByParity(nums)); // Output: [2, 4, 3, 1] |
| 175 | +``` |
| 176 | + |
| 177 | +## Step-by-Step Algorithm |
| 178 | + |
| 179 | +1. Initialize two empty lists/arrays: one for even integers and one for odd integers. |
| 180 | +2. Iterate through the given array: |
| 181 | + - If the current integer is even, add it to the even list/array. |
| 182 | + - If the current integer is odd, add it to the odd list/array. |
| 183 | +3. Concatenate the even list/array with the odd list/array. |
| 184 | +4. Return the concatenated list/array. |
| 185 | + |
| 186 | +## Conclusion |
| 187 | + |
| 188 | +This problem can be solved efficiently by iterating through the array once and separating the integers into even and odd lists/arrays. The time complexity is O(n), where n is the length of the array, making this approach optimal for the given constraints. |
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