Exponentiation

#include <bits/stdc++.h>
#include <bitset>
#include <climits>
using namespace std;
#define all(x) (x).begin(), (x).end()
#define mp make_pair
#define fi first
#define se second
#define pb push_back
#define IOS ios_base::sync_with_stdio(0), cin.tie(0)
const int INF = 1001001001;
const int MAXN = 100'000;
const char br = '\n';
using ll = long long;
using vi = vector<int>;
using pii = pair<int, int>;

int nxt() {
	int x;
	cin >> x;
	return x;
}

unsigned exp_by_squaring(size_t a, size_t b) {
	bitset<INT_WIDTH> e(b);
	size_t msb = 0;
	for (size_t i = 0; i <= e.size(); i++) {
		if (e[i]) {
			msb = i;
		}
	}
	constexpr size_t mod = 1E9 + 7;
	auto res = a;
	for (int i = msb - 1; i >= 0; i--) {
		res = res * res % mod;
		if (e[i])
			res = res * a % mod;
	}
	return res;
}

int main() {
	IOS;

	int n = nxt();
	for (int i = 0; i < n; i++) {
		size_t a, b;
		cin >> a >> b;
		cout << exp_by_squaring(a, b) << br;
	}

	return 0;
}

Test 1

Verdict: WRONG ANSWER

Test 2

Verdict: ACCEPTED

Test 3

Verdict: ACCEPTED