Sort Array By Parity

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.

Note:

1. 1 <= A.length <= 5000

2. 0 <= A[i] <= 5000

Solutions

🧠 Cpp

class Solution
{
public:
    vector<int> sortArrayByParity(vector<int>& A)
    {
        if(A.empty())
            return A;

        auto iter0 = begin(A),
             iter1 = --end(A);

        //O(N) two-pointers in-place solution
        while(iter0 < iter1)
        {
            if(*iter0 % 2 == 1 && *iter1 % 2 == 0)
                std::swap(*iter0, *iter1);
            if(*iter0 % 2 == 0)
                ++iter0;
            if(*iter1 % 2 == 1)
                --iter1;
        }

        return A;
    }
};