Submission #173152

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Source Code Expand

#include <map>
#include <set>
#include <list>
#include <cmath>
#include <queue>
#include <stack>
#include <cstdio>
#include <string>
#include <vector>
#include <complex>
#include <cstdlib>
#include <cstring>
#include <numeric>
#include <sstream>
#include <iostream>
#include <algorithm>
#include <functional>

#define mp       make_pair
#define pb       push_back
#define all(x)   (x).begin(),(x).end()
#define rep(i,n) for(int i=0;i<(n);i++)

using namespace std;

typedef    long long          ll;
typedef    unsigned long long ull;
typedef    vector<bool>       vb;
typedef    vector<int>        vi;
typedef    vector<vb>         vvb;
typedef    vector<vi>         vvi;
typedef    pair<int,int>      pii;

const int INF=1<<29;
const double EPS=1e-9;

const int dx[]={1,0,-1,0},dy[]={0,-1,0,1};
const ll mod = 1000000007;
int N;
int A[2020];
ll mod_pow(ll x,ll n){
	ll res = 1;
	while(n > 0){
		if(n & 1)res = (res * x)%mod;
		x = (x * x)%mod;
		n >>=1;
	}
	return res%mod;
}
ll C(int c,int r){

	ll X = 1,Y = 1;
	for(int i = 1;i <=r;i++){
		Y =(Y*i)%mod;
		X =(X*(i + c - r))%mod;
	}
	return X*mod_pow(Y, mod - 2);

}
int main(){
	cin>>N;
	for(int i = 0;i < N;i++){
		cin>>A[i];
	}

	ll ans = 1;
	for(int i = 0;i < N - 1;i++){
		if(A[i]==-1){
			int pre = i;
			int last;
			last = i;
			while(A[last]==-1){
				last++;
			}
			ans =(ans*C(A[last] - A[pre -1] + last - pre,last - pre))%mod;
			i = last;
		}
	}
	cout <<ans%mod<<endl;
	return 0;
}

Submission Info

Judge Result