洛谷2822(NOIP2016)[组合数问题]--杨辉三角

【链接】
洛谷2822

【解题报告】
杨辉三角无脑搞。

#include<cstdio>using namespace std;const int maxn=2005;int n,k,a[maxn][maxn],f[maxn][maxn];inline char nc(){    static char buf[100000],*l,*r;    if (l==r) r=(l=buf)+fread(buf,1,100000,stdin);    if (l==r) return EOF; return *l++;}inline int Read(){    int res=0; char ch=nc();    while (ch<'0'||ch>'9') ch=nc();    while (ch>='0'&&ch<='9') res=res*10+ch-48,ch=nc();    return res;}int main(){    freopen("2822.in","r",stdin);    freopen("2822.out","w",stdout);    n=Read(); k=Read();    for (int i=0; i<=2000; i++) a[i][i]=a[i][0]=1;    for (int i=1; i<=2000; i++)     for (int j=1; j<=i; j++)      a[i][j]=(a[i-1][j]+a[i-1][j-1])%k;    for (int i=1; i<=2000; i++)     for (int j=1; j<=2000; j++)      {        f[i][j]=f[i][j-1]+f[i-1][j]-f[i-1][j-1];        if (!a[i][j]&&j<=i) f[i][j]++;      }    for (int i=1,x,y; i<=n; i++) x=Read(),y=Read(),printf("%d\n",f[x][y]);    return 0;}