#1152. 【2.15省选联考（广东实验）T1】取石子

https://sjzezoj.com/submission/70245

S2OJ/1152/1152.cpp

@@ -0,0 +1,100 @@
+#include <iostream>
+#include <algorithm>
+#include <functional>
+#include <iterator>
+#include <vector>
+
+using std::cin;
+using std::cout;
+const char endl = '\n';
+
+const int N = 1e5 + 5;
+const int mod = 1e9 + 7;
+
+int n, a, b, winner,
+    cnt_le_a, cnt_le_b, cnt_le_2a, cnt_rest,
+    ans_winner, ans_first, ans_second;
+int fac[N], inv[N], fac_inv[N];
+std::vector<int> v;
+
+enum Winner {
+    Alice = 0,
+    Bob = 1,
+};
+
+int C(int n, int m) {
+    if (n < m || n < 0 || m < 0) return 0;
+    return static_cast<long long>(fac[n]) * fac_inv[m] % mod * fac_inv[n - m] % mod;
+}
+
+constexpr int binpow(int a, int b, int mod = ::mod) {
+    int res = 1;
+    a %= mod;
+
+    while (b) {
+        if (b & 1) res = static_cast<long long>(res) * a % mod;
+        a = static_cast<long long>(a) * a % mod;
+        b >>= 1;
+    }
+
+    return res;
+}
+
+int main() {
+    std::ios::sync_with_stdio(false);
+    cin.tie(nullptr);
+
+    fac[0] = 1;
+    for (int i = 1; i < N; i++) {
+        fac[i] = static_cast<long long>(fac[i - 1]) * i % mod;
+    }
+
+    inv[0] = inv[1] = 1;
+    for (int i = 2; i < N; i++) {
+        inv[i] = static_cast<long long>(mod - (mod / i)) * inv[mod % i] % mod;
+    }
+
+    fac_inv[0] = fac_inv[1] = 1;
+    for (int i = 2; i < N; i++) {
+        fac_inv[i] = static_cast<long long>(fac_inv[i - 1]) * inv[i] % mod;
+    }
+
+    cin >> n >> a >> b;
+
+    if (a < b) {
+        winner = Winner::Alice;
+    } else {
+        std::swap(a, b);
+        winner = Winner::Bob;
+    }
+
+    std::copy_n(std::istream_iterator<int>(cin), n, std::back_inserter(v));
+    std::transform(v.begin(), v.end(), v.begin(), std::bind(std::modulus<int>(), std::placeholders::_1, a + b));
+    std::for_each(v.begin(), v.end(), [&](int x) {
+        if (x < a) cnt_le_a++;            // [1, a)
+        else if (x < b) cnt_le_b++;       // [a, b)
+        else if (x < 2 * a) cnt_le_2a++;  // [b, 2a)
+        else cnt_rest++;                  // [2a, a + b)
+    });
+
+    for (int i = 0; i <= cnt_le_2a; i++) {
+        if (i % 2 == 0) {
+            ans_first = (static_cast<long long>(ans_first) + static_cast<long long>(C(cnt_le_2a, i)) * cnt_rest % mod) % mod;
+            ans_second = (static_cast<long long>(ans_second) + C(cnt_le_2a, i)) % mod;
+        } else {  // i % 2 == 1
+            ans_first = (static_cast<long long>(ans_first) + C(cnt_le_2a, i)) % mod;
+        }
+    }
+
+    ans_first = static_cast<long long>(ans_first) * binpow(2, cnt_le_a) % mod;
+    ans_second = static_cast<long long>(ans_second) * binpow(2, cnt_le_a) % mod;
+    ans_winner = ((static_cast<long long>(binpow(2, n)) - ans_first - ans_second) % mod + mod) % mod;
+
+    if (winner == Winner::Alice) {
+        cout << ans_winner << ' ' << 0 << ' ' << ans_first << ' ' << ans_second << endl;
+    } else {
+        cout << 0 << ' ' << ans_winner << ' ' << ans_first << ' ' << ans_second << endl;
+    }
+
+    return 0;
+}