Submission #635382

#	Time	Username	Problem	Language	Result	Execution time	Memory
635382		Mahdi	Sumtree (INOI20_sumtree)	C++17	10 / 100	8 ms	4196 KiB

Main

#include<bits/stdc++.h>
#pragma GCC optimize("Ofast")
using namespace std;
#define all(v) v.begin(), v.end()
#define F first
#define S second
typedef long long ll;
typedef pair<int, int> pii;
const int N=5e5+5, M=1e9+7;
int n, r, f[N], rf[N];

int tav(int a, int b){
    int res=1;
    while(b){
        if(b&1)
            res=1LL*res*a%M;
        a=1LL*a*a%M;
        b>>=1;
    }
    return res;
}

int C(int x, int y){
    ll res=1LL*f[x]*rf[y]%M;
    res=res*rf[x-y]%M;
    return res;
}

int main(){
    cin>>n>>r;
    f[0]=1;
    for(int i=1;i<N;++i)
        f[i]=1LL*f[i-1]*i%M;
    rf[N-1]=tav(f[N-1], M-2);
    for(int i=N-2;i>=0;--i)
        rf[i]=1LL*(i+1)*rf[i+1]%M;
    cout<<C(r+n-1, n-1)<<'\n';
}

• Subtask 1: 10 / 10
• Subtask 2: 0 / 20
• Subtask 3: 0 / 20
• Subtask 4: 0 / 20
• Subtask 5: 0 / 30