Different Output

Today,there was a coding round for internship in our collage.I wrote a code which was giving different output for same test case on ideone and Hackerrank.On ideone output was 4 and on hackerrank output
 was 0.I don't why??can anyone explain.
here is that test case and  my code ...
4 1
2
3
5
7


#include <iostream>
using namespace std;
int main() {
        int s,g;
        cin>>s>>g;
        int arr[s];
        int c=g;
        for(int i=0;i<s;i++)
        cin>>arr[i];
        int len=1;
        int val=0;
        for(int i=1;i<s;i++)
        {
            if(arr[i]==arr[i-1]+1)
            len++;
            else if(arr[i]-arr[i-1]<=g+1)
            {
                len+=(arr[i]-arr[i-1]);
                g=g-(arr[i]-arr[i-1]);
            }
            else
            {
                if(val<len)
                val=len;
                len=1;
                //g=c;
            }
        }
        if(val<len)
        val=len;
            cout<<val<<endl;
    return 0;

}