Given a non-empty 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?
Example 1:
Input: [2,2,1]
Output: 1
Example 2:
Input: [4,1,2,1,2]
Output: 4
题目:找出只出现过一次的数字。
思路:可以用哈希表索引计数;或者排序,从头开始搜索;最简单的方法是异或。
代码:
class Solution {
public:
int singleNumber(vector<int>& nums) {
int ans = 0;
for (auto &i : nums) ans ^= i;
return ans;
}
};