Divisible subarray test cases

#1

#include
using namespace std;
typedef long long ll;
int pre[100000];
int main()
{
int T;
cin >> T;
while(T–){
ll n;
cin>>n;
ll arr[n];
for(ll i=0;i<n;i++)
cin>>arr[i];
ll sum = 0;

pre[0] = 1;
for (ll i = 0; i < n; i++) {

	sum += arr[i];
	sum %= n;

	sum = (sum + n) % n;

	pre[sum]++;

}
ll ans = 0;
for (ll i = 0; i < n; i++)
{
	ll m = pre[i];

	if (m >= 2)
	{
		ans = (m) * (m - 1) / 2;
	}


}
cout << ans << endl;

}
return 0;
}
i am getting passed only one test case.why?

#2

hello @dare_devil_007
a)

apply modular arithmetic property
i.e sum=(sum+arr[i])%n

b)

it should be ans=ans + m*(m-1)/2

#3

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