# Longest Sub-Array with Sum K | GFG Solution

## Longest Sub-Array with Sum K  | GFG Solution

Given an array containing N integers and an integer K., Your task is to find the length of the longest Sub-Array with the sum of the elements equal to the given value K.

Example 1:

```Input :
A[] = {10, 5, 2, 7, 1, 9}
K = 15
Output : 4
Explanation:
The sub-array is {5, 2, 7, 1}.
```

Example 2:

```Input :
A[] = {-1, 2, 3}
K = 6
Output : 0

```

This is a function problem. The input is already taken care of by the driver code. You only need to complete the function smallestSubsegment() that takes an array (A), sizeOfArray (n),  sum (K)and returns the required length of the longest Sub-Array
. The driver code takes care of the printing.

Expected Time Complexity: O(N).
Expected Auxiliary Space: O(N).

Constraints:
1<=N<=105
-105<=A[i], K<=105

// { Driver Code Starts
#include <bits/stdc++.h>
using namespace std;

// } Driver Code Ends

class Solution{
public:
int lenOfLongSubarr(int A[],  int N, int K)
{
unordered_map<int,int>m;
int sum=0,ans=0;
m=0;
for(int i=0; i<N; i++){
sum+=A[i];
if(sum==K)ans=i+1;
if(m[sum]==0)m[sum]=i+1;
if(m[sum-K]>0)ans=max(ans,i-m[sum-K]+1);
}
return ans;
}

};

// { Driver Code Starts.

int main() {
//code

int t;cin>>t;
while(t--)
{
int n, k;
cin>> n >> k;
int a[n];

for(int i=0;i<n;i++)
cin>>a[i];
Solution ob;
cout << ob.lenOfLongSubarr(a, n , k)<< endl;

}

return 0;
}  // } Driver Code Ends