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?
public int singleNumber(int[] A) { // Note: The Solution object is instantiated only once and is reused by each test case. int n = A.length; if(n<0)return -1; int res = 0; for(int i =0;i<n;i++) res ^= A[i]; return res; }