P5596 【XR-4】题

https://www.luogu.com.cn/record/76300560

Luogu/P5596/P5596.cpp

@@ -0,0 +1,61 @@
+#include <cmath>
+#include <iostream>
+
+using std::cin;
+using std::cout;
+const char endl = '\n';
+
+long long a, b, d, m, ans;
+
+int main() {
+    std::ios::sync_with_stdio(false);
+
+    cin >> a >> b;
+
+    d = a * a - b * 4;
+
+    if (d == 0) {
+        cout << "inf" << endl;
+
+        exit(0);
+    } else if (d < 0) {
+        d *= -1;
+        m = std::sqrt(d);
+
+        for (long long q = 1; q <= m; q++) {
+            if (d % q == 0) {
+                long long p = d / q;
+
+                long long x = p - q - 2 * a,
+                          y = p + q;
+
+                if (x % 4 || y % 4) continue;
+
+                x /= 4, y /= 4;
+
+                if (x >= 0 && y >= x) ans++;
+            }
+        }
+    } else {  // d > 0
+        m = std::sqrt(d);
+
+        for (long long q = 1; q <= m; q++) {
+            if (d % q == 0) {
+                long long p = d / q;
+
+                long long x = p + q - 2 * a,
+                          y = p - q;
+
+                if (x % 4 || y % 4) continue;
+
+                x /= 4, y /= 4;
+
+                if (x >= 0 && y >= x) ans++;
+            }
+        }
+    }
+
+    cout << ans << endl;
+
+    return 0;
+}