P1495 【模板】中国剩余定理(CRT)/曹冲养猪

https://www.luogu.com.cn/record/74538615

Luogu/P1495/P1495.cpp

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+#include <iostream>
+
+using std::cin;
+using std::cout;
+const char endl = '\n';
+
+const int N = 1e5 + 5;
+
+int n;
+long long a[N], b[N];
+
+long long exgcd(long long a, long long b, long long &x, long long &y) {
+    if (!b) {
+        x = 1, y = 0;
+        return a;
+    }
+
+    long long g = exgcd(b, a % b, y, x);
+    y -= a / b * x;
+
+    return g;
+}
+
+long long CRT() {
+    long long mod = 1, ans = 0;
+
+    for (int i = 1; i <= n; i++) {
+        mod *= a[i];
+    }
+
+    for (int i = 1; i <= n; i++) {
+        long long m = mod / a[i], x, y;
+        exgcd(m, a[i], x, y);
+        ans = (ans + b[i] * m * x % mod) % mod;
+    }
+
+    return (ans % mod + mod) % mod;
+}
+
+int main() {
+    std::ios::sync_with_stdio(false);
+
+    cin >> n;
+
+    for (int i = 1; i <= n; i++) {
+        cin >> a[i] >> b[i];
+    }
+
+    cout << CRT() << endl;
+
+    return 0;
+}