Leetcode Single Number

Given an array of integers, every element appears twice except for one. Find that single one.

Note:
Your algorithm should have a linear runtime complexity. Could you implement it without using extra memory?

此題考慮位運算求解

a^a = 0

0^a = 0

int singleNumber(int A[], int n){
    int res = 0;
    for(int i = 0 ; i < n ; ++ i )
        res^=A[i];
    return res;
}