Tom and matrix HDU

Tom and matrix

 HDU - 5226 

题意：就是求组合数~

第一道Lucas定理的题。

参考http://www.cnblogs.com/ykzou/p/4494969.html

#include <bits/stdc++.h>
using namespace std;
#define ll long long
const int maxn=100010;
ll fac[maxn];
ll x1,x2;
ll p;
ll Y1,Y2;
void init(){
    fac[0]=1;
    for(int i=1;i<maxn;i++) fac[i]=fac[i-1]*i%p;
}

ll quickpow(ll a,ll b,ll p){
    ll temp=a%p,res=1;
    while(b){
        if(b&1) res=(res*temp)%p;
        b>>=1;
        temp=(temp*temp)%p;
    }
    return res;
}
ll cal(ll n,ll m){
    if(m>n) return 0;
    return fac[n]*quickpow(fac[m]*fac[n-m],p-2,p)%p;
}
ll Lucas(ll n,ll m){
    if(m==0) return 1;
    return cal(n%p,m%p)*Lucas(n/p,m/p)%p;
}

int main(){

    while(scanf("%lld%lld%lld%lld%lld",&x1,&Y1,&x2,&Y2,&p)!=EOF){
        init();
        ll ans=0;
        for(ll i=Y1;i<=Y2;i++){
            ans=(ans+Lucas(x2+1,i+1)-Lucas(x1,i+1)+p)%p;
        }
        printf("%lld
",ans);
    }
}