260. Single Number III

Total Accepted: 30927 Total Submissions: 71149 Difficulty: Medium

Given an array of numbers nums, in which exactly two elements appear only once and all the other elements appear exactly twice. Find the two elements that appear only once.

For example:

Given nums = [1, 2, 1, 3, 2, 5], return [3, 5].

Note:

The order of the result is not important. So in the above example, [5, 3] is also correct.
Your algorithm should run in linear runtime complexity. Could you implement it using only constant space complexity?

Code:

/**
* Return an array of size *returnSize.
* Note: The returned array must be malloced, assume caller calls free().
*/
int* singleNumber(int* nums, int numsSize, int* returnSize) {
    int num = 0;
    int i;
    int *tmp = (int*)malloc(2*sizeof(int));
    for(i = 0;i<numsSize;i++)
        num ^= nums[i];
    int lowBit = 1;
    while(!(lowBit&num))
    {
        lowBit<<=1;
    }
    tmp[0] = 0;
    tmp[1] = 0;
    for(i = 0;i<numsSize;i++)
    {
        if((nums[i]&lowBit) != 0)
        {
            tmp[0] ^= nums[i];
        }
        else
        {
            tmp[1] ^= nums[i];
        }
    }
    *returnSize = 2;
    return tmp;
}