# Kadane's Algorithm

Given an array of N integers. Find the contiguous sub-array(containing at least one number) which has the maximum sum and return its sum.


Example 1:

Input:
N = 5
Arr[] = {1,2,3,-2,5}
Output:
9
Explanation:
Max subarray sum is 9
of elements (1, 2, 3, -2, 5) which 
is a contiguous subarray.
Example 2:

Input:
N = 4
Arr[] = {-1,-2,-3,-4}
Output:
-1
Explanation:
Max subarray sum is -1 
of element (-1)


In this using kadane's algo we can find longest contigious subarray we have to keep track of 2 varables current maximum and the max so far and we will update max so far as we traverse the array with max of current maximum.


```

#include<bits/stdc++.h>
using namespace std;
class Solution{
    public:
    // arr: input array
    // n: size of array
    //Function to find the sum of contiguous subarray with maximum sum.
    long long maxSubarraySum(int arr[], int n){
        
        // Your code here
        long long cs=arr[0],ms=arr[0],a;
        for(int i=1;i<n;i++)
        {
            a=arr[i];
            cs=max(cs+a,a);
            ms=max(ms,cs);
        }
        
        return ms;
    }
};

int main()
{
    int t,n;
    
    cin>>t; //input testcases
    while(t--) 
    {
        
        cin>>n; 
        
        int a[n];
        
        for(int i=0;i<n;i++)
            cin>>a[i]; 
            
        Solution ob;
        
        cout << ob.maxSubarraySum(a, n) << endl;
    }
}
 
```