【LeetCode】136. Single Number

Difficulty:easy

 More:【目錄】LeetCode Java實現

Description

https://leetcode.com/problems/single-number/

Given a non-empty 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?

Example 1:

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

Example 2:

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

Intuition

use XOR ( ^ )

 

Solution

    public int singleNumber(int[] nums) {
        int ans=0;
        for(int n : nums){
            ans=ans^n;
        }
        return ans;
    }

　　

Complexity

Time complexity : O(n)

Space complexity : O(1)

 

What I've learned

1. when meeting problems about duplicate, considering using XOR.

 

 More:【目錄】LeetCode Java實現