P1516 青蛙的约会

https://www.luogu.com.cn/record/74258790

Luogu/P1516/P1516.cpp

@@ -0,0 +1,46 @@
+#include <iostream>
+
+using std::cin;
+using std::cout;
+const char endl = '\n';
+
+long long x, y, n, m, l;
+
+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, x, y);
+    long long t = x;
+    x = y;
+    y = t - a / b * y;
+    return g;
+}
+
+int main() {
+    std::ios::sync_with_stdio(false);
+
+    cin >> x >> y >> m >> n >> l;
+
+    long long b = n - m,
+              c = x - y,
+              xx, yy;
+
+    if (b < 0) {
+        b = -b;
+        c = -c;
+    }
+
+    long long g = exgcd(b, l, xx, yy);
+
+    if (c % g) {
+        cout << "Impossible" << endl;
+    } else {
+        cout << (c / g * xx % (l / g) + (l / g)) % (l / g) << endl;
+    }
+
+    return 0;
+}