P2822 [NOIP2016 提高组] 组合数问题

https://www.luogu.com.cn/record/80088595

Luogu/P2822/P2822.cpp

@@ -0,0 +1,41 @@
+#include <iostream>
+
+using std::cin;
+using std::cout;
+const char endl = '\n';
+
+const int N = 2005;
+
+int t, k, n, m, c[N][N], f[N][N];
+
+int main() {
+    cin >> t >> k;
+
+    c[1][1] = 1;
+    for (int i = 1; i <= 2000; i++) {
+        c[i][0] = c[i][i] = 1;
+    }
+
+    for (int i = 2; i <= 2000; i++) {
+        for (int j = 1; j < i; j++) {
+            c[i][j] = (c[i - 1][j] + c[i - 1][j - 1]) % k;
+        }
+    }
+
+    for (int i = 1; i <= 2000; i++) {
+        for (int j = 1; j <= i; j++) {
+            f[i][j] = f[i][j - 1] + f[i - 1][j] - f[i - 1][j - 1];
+            if (!c[i][j]) f[i][j]++;
+        }
+
+        f[i][i + 1] = f[i][i];
+    }
+
+    while (t--) {
+        cin >> n >> m;
+
+        cout << f[n][std::min(n, m)] << endl;
+    }
+
+    return 0;
+}