leetcode -- single number

2019独角兽企业重金招聘Python工程师标准>>>

Single Number

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?

Solution

    public int singleNumber(int[] nums) {
        int re = 0;
        for(int i=0; i< nums.length; i++ ){
            re ^= nums[i];
        }
        return re;
    }

这里使用异或的方法。 比如输入的数组是 {1， 2， 3， 4， 2， 3， 1}

re = 0^1^2^3^4^2^3^1
    =0^(1^1)^(2^2)^(3^3)^4
    =0^0^0^0^4
    =0^4
    =4

转载于:https://my.oschina.net/u/1447519/blog/1596544