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?
异或即可处理，而且，不仅能处理两次的情况，只要出现偶数次，都可以清零。
1 class Solution { 2 public: 3 int singleNumber(int A[], int n) { 4 5 int res = 0; 6 7 for(int i = 0; i<n; i++) 8 { 9 res = res ^ A[i]; 10 } 11 12 return res; 13 } 14 };
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原文：http://www.cnblogs.com/diegodu/p/3812797.html