# Longest Harmonious Subsequence in C++

C++Server Side ProgrammingProgramming

Suppose we have an integer array; we have to find the length of its longest harmonious subsequence among all its possible subsequences. As we know a harmonious sequence array is an array where the difference between its maximum value and its minimum value is exactly 1.

So, if the input is like [1,3,2,2,5,2,3,7], then the output will be 5, as the longest harmonious subsequence is [4,3,3,3,4].

To solve this, we will follow these steps −

• Define one map m

• for n in nums −

• (increase m[n] by 1)

• for key-value pair (k,v) in m −

• it := position of (k+1) in m

• if 'it' is in m, then −

• max_:= maximum of max_ and value of it

• return max_

## Example

Let us see the following implementation to get a better understanding −

Live Demo

#include <bits/stdc++.h>
using namespace std;
class Solution {
public:
int findLHS(vector<int>& nums) {
unordered_map<int, int> m;
for (const int n : nums)
++m[n];
int max_{ 0 };
for (const auto & [ k, v ] : m) {
auto it = m.find(k + 1);
if (it != m.end())
max_ = max(max_, v + it->second);
}
return max_;
}
};
main(){
Solution ob;
vector<int> v = {2,4,3,3,6,3,4,8};
cout << (ob.findLHS(v));
}

## Input

{2,4,3,3,6,3,4,8}

## Output

5