[LeetCode]594. Longest Harmonious Subsequence<HashMap>

We define a harmonious array is an array where the difference between its maximum value and its minimum value is exactly 1.

Now, given an integer array, you need to find the length of its longest harmonious subsequence among all its possible subsequences.

Example 1:

Input: [1,3,2,2,5,2,3,7]Output: 5Explanation: The longest harmonious subsequence is [3,2,2,2,3].

Note: The length of the input array will not exceed 20,000.

public class Solution {    public int findLHS(int[] nums) {        Map<Integer, Integer> map = new HashMap<>();        for(int num: nums)            map.put(num , map.getOrDefault(num,0)+1);                int res=0;        for(int num: map.keySet()){            if(map.containsKey(num+1))                res=Math.max(res, map.get(num)+map.get(num+1));        }                return res;    }}

注意getOrDefauld()的用法。

返回map键对应的map值，如果不存在map键，返回默认值。

for(int num: map.keySet())