Submission #4026703

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Source Code Expand

#include <iostream>
#include <cassert>
using namespace std;
typedef long long ll;
int R,C,X,Y,D,L;

ll inf = 1e9+7;
ll func[910] = {0};
ll inv[910] = {0};

ll mult(ll n, ll m){
	if(m==1) return n%inf;
	else if(m%2==0){
		ll t = mult(n,m/2);
		return (t*t)%inf;
	}else{
		ll t = mult(n,m-1);
		return (t*n)%inf;
	}
}

void factorial(ll N){
	for(ll i=0;i<=N;i++){
		if(i==0){
			func[i] = 1;
			inv[i] = 1;
		}
		else{
			func[i] = (i*func[i-1])%inf;
			inv[i] = mult(func[i],inf-2);
		}
	}
}

ll comb(ll n,ll k){
	if(n<k) return 0;
	if(k==0 || n==k) return 1;
	else return (((func[n]*inv[k])%inf)*inv[n-k])%inf;
}


int main(){
	cin >> R >> C >> X >> Y >> D >> L;
	factorial(X*Y);
	ll ans = (comb(X*Y,D)*comb(X*Y-D,L))%inf,sub = 0;
	(sub += 2*(comb(X*(Y-1),D)*comb(X*(Y-1)-D,L))%inf + 2*(comb(Y*(X-1),D)*comb(Y*(X-1)-D,L))%inf)%=inf;
	sub -= (comb(X*(Y-2),D)*comb(X*(Y-2)-D,L))%inf + (comb(Y*(X-2),D)*comb(Y*(X-2)-D,L))%inf;
	(sub += 2*inf)%=inf;
	assert(sub>=0);
	sub -= 2*(comb((X-1)*(Y-1),D)*comb((X-1)*(Y-1)-D,L))%inf + 2*(comb((Y-1)*(X-1),D)*comb((Y-1)*(X-1)-D,L))%inf;
	(sub += 2*inf)%=inf;
	assert(sub>=0);
	(sub += 2*(comb((X-1)*(Y-2),D)*comb((X-1)*(Y-2)-D,L))%inf + 2*comb((Y-1)*(X-2),D)*comb((Y-1)*(X-2)-D,L))%=inf;
	if(X>=2 || Y>=2) sub -= (comb((X-2)*(Y-2),D)*comb((X-2)*(Y-2)-D,L))%inf;
	(sub += 2*inf)%=inf;
	assert(sub>=0);
	(ans += -sub+inf)%inf;
	cout << (ans*(R-X+1)*(C-Y+1))%inf << endl;
}

Submission Info

Judge Result