P2822 组合数问题
递推加动规,就酱紫
#include<set> #include<map> #include<list> #include<queue> #include<stack> #include<string> #include<cmath> #include<ctime> #include<vector> #include<bitset> #include<memory> #include<utility> #include<cstdio> #include<sstream> #include<iostream> #include<cstdlib> #include<cstring> #include<algorithm> using namespace std; int n,m,k,t; int a[2005][2005],f[2005][2005]; int ff(){ a[1][1]=a[1][0]=1; for(int i=2;i<=2000;i++){ a[i][0]=1; for(int j=1;j<=i;j++){ a[i][j]=(a[i-1][j]+a[i-1][j-1])%k; } } for(int i=2;i<=2000;i++){ for(int j=1;j<=i;j++){ f[i][j]=f[i-1][j]+f[i][j-1]-f[i-1][j-1]; if(a[i][j]==0){ f[i][j]+=1; } } f[i][i+1]=f[i][i]; } } int main(){ //freopen("problem.in","r",stdin); //freopen("problem.out","w",stdout); scanf("%d%d",&t,&k); ff(); while(t--){ scanf("%d%d",&n,&m); if(m>n){ m=n; } printf("%d\n",f[n][m]); } return 0; }
嗯好的就这样