Numbers that only appear once

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title: A number that appears only once （ Water is a simple problem ）
date: 2022-05-04 19:59:40
tags: Make a little progress every day

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subject

subject ： A number that appears only once

Given an array of non-empty integers , Except that an element only appears once , Each of the other elements occurs twice . Find the element that only appears once .

explain ： Your algorithm should have linear time complexity . Can you do this without using extra space ？

Example 1:

 Input : [2,2,1] Output : 1

Example 2:

 Input : [4,1,2,1,2] Output : 4

Answer key ：

You can use XOR directly (^, Same as 0, Different for 1) To solve the , Let's start with the plan , All numbers in the XOR array , The last thing left is the number that appears only once

analysis ：

a^a = 0 0^b = b , therefore a^a ^ b = b

Take a number for example ：

3 ^ 3 = 0011^0011 = 0000 = 0

0 ^ 2 = 0000^0010 = 0010 = 2

therefore 3^3 ^2 = 2

Finally, after all the even number of exclusive or, it becomes 0 了 ,0 In and once （ In fact, the same is true for odd times ） Exclusive or , What we get is the number we want

Code ：

class Solution {    public int singleNumber(int[] nums) {        // Using XOR  , because  a^b^a = b         int res = 0;        for (int num : nums) {            // therefore             res ^= num;        }        return res;    }}

These are the numbers that only appear once 【LeetCode】 The whole content of

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