LeetCode之Missing Number

1、题目

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

 

 

2、代码实现

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;
    }
}

 

 

 

3、注意的地方

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