Leetcode算法学习日志-594 Longest Harmonious Subsequence

Leetcode 594 Longest Harmonious Subsequence

题目原文

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

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

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.

题意分析

给定一串序列，找出一个最长子序列，使得最大和最小值之间差距刚好为1.关键在于刚好为1，也就是说子序列中只有两种相差1的元素。

解法分析

由于所需子序列有且只有两种元素，且相差为1，所以可以用map将所有数字的个数记录下来，再遍历map，如果对于一个key，如果key+1也存在于map中，则存在以key和key+1两个数字组成的和谐子序列，长度为两个数字的个数之和。C++代码如下：

class Solution {public:    int findLHS(vector<int>& nums) {        map<int,int> myCount;        int res=0;        int temp;        for(int i=0;i<nums.size();i++)            myCount[nums[i]]++;        for(auto N:myCount)            res=(myCount.count(N.first+1))?max(res,N.second+myCount[N.first+1]):res;        return res;       }};