HDU 6311 Harvest of Apples (組合數，莫隊)

標籤：turn   style   while   組合數   dea   mat   res   begin   cto   

場上怎麼都想不出來，看了標程想自閉。。。

#include <algorithm>#include <iostream>#include <cstdio>#include <vector>#include <cmath>using namespace std;#define N 100005#define mod 1000000007struct query{    int n,k,i;}Q[N];bool cmp(const query&a,const query&b){    return a.n<b.n;}int reflect[N];///分塊vector<query>lis[2000];int fac[N],inv[N];int quick(int a,int b){    int odd = 1;    while (b){        if(b&1)odd = 1ll*odd*a%mod;        a = 1ll*a*a%mod;        b>>=1;    }    return odd;}const int mx = 100000;void deal(){    fac[0] = 1;    for(int i = 1 ; i <= mx ; ++i){        fac[i] = 1ll*i*fac[i-1]%mod;    }    inv[mx] = quick(fac[mx],mod-2);    for(int i = mx ; i ; --i){        inv[i-1] = 1ll*i*inv[i]%mod;    }}int res[N];int C(int n,int m){    return 1ll*fac[n]*inv[m]%mod*inv[n-m]%mod;}int main() {    deal();    int cent = sqrt(mx);    int cnt = 1;    for (int i = 1; i <= mx; i += cent, ++cnt) {        for (int j = i; j <= mx and j <= i + cent; ++j) {            reflect[j] = cnt;        }    }    int T;    scanf("%d",&T);    for(int i = 1 ; i <= T ; ++i){        scanf("%d %d",&Q[i].n,&Q[i].k);        Q[i].i = i;        lis[reflect[Q[i].k]].push_back(Q[i]);    }    for(int i = 1 ; i <= cnt ; ++i)if(!lis[i].empty()){        sort(lis[i].begin(),lis[i].end(),cmp);        int val = 0,in = lis[i][0].n,ik = -1;        for(auto &j : lis[i]){            while (in<j.n)val = (0ll + val + val + mod - C(in++,ik))%mod;            while (ik<j.k)val = (val + C(in,++ik))%mod;            while (ik>j.k)val = (val + mod - C(in,ik--))%mod;            res[j.i] = val;        }    }    for(int i = 1 ; i <= T ; ++i){        printf("%d\n",res[i]);    }}

標程太秀了，頂禮膜拜。

HDU 6311 Harvest of Apples (組合數，莫隊)