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Longest Harmonious Subsequence in C++
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 −
#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
Updated on: 11-Jun-2020
372 Views
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