Single Number
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
class Solution {
public:
//异或
// 1 ^ 1 = 0
int singleNumber(vector<int>& nums) {
int res = nums[0];
for(int i=1;i<nums.size();i++){
res ^= nums[i];
}
return res;
}
};
或者利用hash表