update

src/P2822/P2822_prefix.cpp

@@ -0,0 +1,34 @@
+#include <iostream>
+#include <algorithm>
+
+using ull = unsigned long long;
+
+static constexpr size_t max_n {(size_t)2e3+5}; 
+
+ull k, c[max_n][max_n], prefix[max_n][max_n], t, n, m;
+
+static void init(){
+    c[0][0] = c[1][0] = c[1][1] = 1;
+    for(ull i {2};i<max_n;i++){
+        c[i][0]=1;
+        for(ull j{1};j<max_n;j++){
+            c[i][j] = (c[i-1][j-1] + c[i-1][j])%k;
+        }
+    }
+    for(ull i {2};i<max_n;i++){
+        for(ull j{1};j<=i;j++){
+            prefix[i][j] = prefix[i-1][j]+prefix[i][j-1]-prefix[i-1][j-1] + (c[i][j]==0?1:0);
+        }
+        prefix[i][i+1] = prefix[i][i];
+    }
+}   
+
+int main(){
+    std::cin>>t>>k;
+    init();
+    for(ull i {0};i<t;i++){
+        std::cin>>n>>m;
+        m = std::min(m,n);
+        std::cout<<(prefix[n][m])<<'\n';
+    }
+}