[20251106] BOJ / G1 / XOR Hashing / 권혁준

Author: oncsr

khj20006/202511/06 BOJ G1 XOR Hashing.md

@@ -0,0 +1,31 @@
+```cpp
+#include <bits/stdc++.h>
+using namespace std;
+using ll = long long;
+
+const ll MOD = 1e9 + 7;
+ll N, M;
+
+ll power(ll a, ll b) {
+	if (b == 0) return 1;
+	if (b == 1) return a % MOD;
+	ll h = power(a, b >> 1) % MOD;
+	h = h * h % MOD;
+	return (b & 1) ? h * a % MOD : h;
+}
+
+int main() {
+	cin.tie(0)->sync_with_stdio(0);
+
+	cin >> N >> M;
+	N = (1 << N);
+	if (M > N) return cout << 1, 0;
+
+	ll g = power(N, M), p = 1;
+	for (ll i = N; i > N - M; i--) p = (p * i) % MOD;
+
+	ll ans = ((g - p + MOD) % MOD) * power(g, MOD - 2) % MOD;
+	cout << ans;
+
+}
+```