905. Sort Array By Parity

Given an array A of non-negative integers, return an array consisting of all the even elements of A, followed by all the odd elements of A.

You may return any answer array that satisfies this condition.

Example 1:

Input: [3,1,2,4]
Output: [2,4,3,1]
The outputs [4,2,3,1], [2,4,1,3], and [4,2,1,3] would also be accepted.

解题要点：

设置一个新的数组，先遍历一遍旧数组，如有偶数，加进新数组；再遍历一遍，把奇数也加进数组。

class Solution {
    public int[] sortArrayByParity(int[] A) {
        int count = 0;
        int[] res = new int[A.length];
        
        for(int a : A) if(a % 2 == 0) res[count++] = a;
        for(int a : A) if(a % 2 == 1) res[count++] = a;
        
        return res;        
    }
}