LeetCode每日一题——Single Number

一、题目

136. Single Number

Given a non-empty array of integers nums, every element appears twice except for one. Find that single one.

You must implement a solution with a linear runtime complexity and use only constant extra space.

Example 1:

Input: nums = [2,2,1]
Output: 1
Example 2:

Input: nums = [4,1,2,1,2]
Output: 4
Example 3:

Input: nums = [1]
Output: 1

Constraints:

1 <= nums.length <= 3 * 104
-3 * 104 <= nums[i] <= 3 * 104
Each element in the array appears twice except for one element which appears only once.

二、题解

位运算异或即可

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