Submission #20027

#	Time	Username	Problem	Language	Result	Execution time	Memory
20027		cki86201	순열 (kriii4_T)	C++14	100 / 100	260 ms	1720 KiB

T

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <memory.h>
#include <math.h>
#include <assert.h>
#include <stack>
#include <queue>
#include <map>
#include <set>
#include <string>
#include <algorithm>
#include <iostream>
#include <functional>
#include <unordered_map>
#include <unordered_set>

using namespace std;
typedef long long ll;
typedef pair<int, int> Pi;
#define Fi first
#define Se second
#define pb(x) push_back(x)
#define sz(x) (int)x.size()
#define rep(i,n) for(int i=0;i<n;i++)
#define all(x) x.begin(),x.end()

const ll MOD = 1e9 + 7;

ll pw(ll x, ll y){
	ll res = 1;
	while(y){
		if(y & 1)res = res * x % MOD;
		x = x * x % MOD;
		y >>= 1;
	}
	return res;
}

int main(){
	ll f = 1;
	int n, k;
	scanf("%d%d", &n, &k);
	if(n == k){
		printf("0");
		return 0;
	}
	for(int i=1;i<=n+1;i++)f = i * f % MOD;
	ll s = 0;
	for(int i=k+1;i<=n;i++){
		s += (n+1-i) * pw(i+1, MOD-2);
		s %= MOD;
	}
	f = f * s % MOD;
	printf("%lld", f);
	return 0;
}

• Subtask 1: 8 / 8
• Subtask 2: 92 / 92