In step 3 , question number 1 : I write two codes very similar to each , As i am a newbie can you help me out to find what is difference in two code. I got ac in one submission and wrong answer in other.

Also if you don not know what difference between two code, give this blog a upvote so many people can see it.

[problem:307094A]

AC : [submission:157416384]

WA : [submission:157415655]

void solve() 
{
	int n, p; cin >> n >> p;
	int sum{}, ans = 0 , res{}, index{}, prefix{};

	vector<int> v(2 * n);
	rep(i, 0, n) {
		cin >> v[i];
		v[i + n] = v[i];
		sum += v[i];
	}

	if (sum < p) {
		res = p / sum * n;
		p %= sum;
	}
	if (p != 0) {
		ans = INT_MAX;
		for (int r = 0, l = 0; r < 2 * n ; r++ ) {
			prefix += v[r];
			while (l < n and prefix >= p) {
				if (ans > r - l + 1) {
					ans = r - l + 1;
					index = l ;
				}
				prefix -= v[l];
				l++;
			}
		}
	}
	cout << index + 1 << " " << ans  + res << endl;


}

WA :

void solve() 
{
	int n, p; cin >> n >> p;
	int sum{}, ans = LLONG_MAX , res{}, index{}, prefix{};

	vector<int> v(2 * n);
	rep(i, 0, n) {
		cin >> v[i];
		v[i + n] = v[i];
		sum += v[i];
	}

	if (sum < p) {
		res = p / sum * n;
		p %= sum;
	}

	for (int r = 0, l = 0; r < 2 * n ; r++ ) {
		prefix += v[r];
		while (l < n and prefix >= p) {
			if (ans > r - l + 1) {
				ans = r - l + 1;
				index = l + 1;
			}
			prefix -= v[l]; l++;
		}
	}

	cout << index << " " << ans  + res << endl;


}

[meanwhile this is my first time here]