Single Number

描述

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?

分析

异或，不仅能处理两次的情况，只要出现偶数次，都可以清零。

代码

Java

// Single Number
// 时间复杂度O(n)，空间复杂度O(1)
public class Solution {
    public int singleNumber(int[] nums) {
        int x = 0;
        for (int i : nums) {
            x ^= i;
        }
        return x;
    }
};

C++

// Single Number
// 时间复杂度O(n)，空间复杂度O(1)
class Solution {
public:
    int singleNumber(vector<int>& nums) {
        int x = 0;
        for (int i : nums) {
            x ^= i;
        }
        return x;
    }
};

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