[LeetCode]Missing Number

Problem Description

[https://leetcode.com/problems/missing-number/]
Given an array containing n distinct numbers taken from 0, 1, 2, …, n, find the one that is missing from the array.

For example,
Given nums = [0, 1, 3] return 2.

思路

求和在一个个减，剩下的就是答案
有了思路很好写，关键是思路从哪来！！！

Code

package q268;public class Solution {    public int missingNumber(int[] nums) {        int m=nums.length;        int ans=(m+1)*m/2;        for(int i=0;i<nums.length;i++){            ans-=nums[i];        }        return ans;    }//  public static void main(String[] args) {//      int[] a={0,1,2,3,4,5};//      Solution s=new Solution();//      System.out.println(s.missingNumber(a));////  }}