LeetCode594. Longest Harmonious Subsequence-优快云博客

本文介绍了一种使用unordered_map解决LeetCode 594题的方法，即寻找数组中最长的和谐子序列，和谐子序列定义为最大值与最小值之差恰好为1的子序列。

LeetCode594. Longest Harmonious Subsequence

题目：

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: 5
Explanation: The longest harmonious subsequence is [3,2,2,2,3].

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

题目分析：

这是一道HashMap的题，是leetcode上easy的题，所以直接用map就可以很简单的解决问题，但是如果要更快一点，可以选择unordered_map，省去了排序的时间。

以下是我的代码：

#include<unordered_map>
using namespace std;
class Solution {
public:
    int findLHS(vector<int>& nums) {
        int max = 0;
        unordered_map<int, int> m;
        for (auto i : nums) {
            m[i]++;
        }
        for (auto i : m) {
            if (m.count(i.first+1) != 0) {
                if(i.second + m[i.first + 1] > max) {
                    max = i.second + m[i.first+1];
                }
            }
            // else
            //     if (i.second > max)
            //         max = i.second;
        }
        return max;
    }
};