LeetCode:Single Number

Single Number

Total Accepted: 98435  Total Submissions: 210216  Difficulty: Medium

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?

Subscribe to see which companies asked this question

Hide Tags

  Hash Table Bit Manipulation

Hide Similar Problems

解题思路：

1.题目要求找出数组中只出现一次的数；

2.xor异或规则：

a^a = 0;

a^0 = a;

所以，对数组N[N1,N1,N2,...,Nk]的异或（假设Ni是唯一的数）：

N1^N1^N2^N2^......^Ni^......^Nk^Nk
=(N1^N1)^(N2^N2)^......^Ni^......^(Nk^Nk)
=0^0^......^Ni^......^0
=Ni

因此，代码如下：

class Solution {
public:
    int singleNumber(vector<int>& nums) {
        int ans = nums[0];
        for(int i=1;i<nums.size();i++) ans^=nums[i];
        return ans;
    }
};