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.

Given nums = [0] return 1

public class Solution {public  int missingNumber(int[] nums) {if (nums == null) {return 0;}int result = 0;Map<Integer, Integer> map = new HashMap<Integer, Integer>();for (int  i = 0;  i < nums.length; ++i) {map.put(nums[i], 2);}for (int i = 0; i <= nums.length; ++i) {Integer in = map.get(i);if (in == null) {return i;}}return result;}
}

 

这个地方需要注意

for (int i = 0; i <= nums.length; ++i) {Integer in = map.get(i);if (in == null) {return i;}}

一定要记得写 i <= nums.length ,不是i < length