Submission #1180310

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Source Code Expand

#include<bits/stdc++.h>
#define N 2005
using namespace std;
const int mo=1e9+7;
int n,m,k,S,f[2*N][N],ans;
void inc(int &x,int y){ x=x+y>=mo ? x+y-mo : x+y;}
void dec(int &x,int y){ x=x-y<0 ? x-y+mo : x-y;}
int main()
{
	int i,j;
	cin>>n>>m>>k;
	f[0][0]=1;
	for(i=1;i<=n+m-1;i++){
		S=0;
		for(j=0;j<=m;j++){
			if(j>=k) dec(S,f[i-1][j-k]);
			if(j%(k-1)==m%(k-1)&&(k-1)*i-j<=n-1&&((k-1)*i-j)%(k-1)==(n-1)%(k-1))
				inc(ans,S);
			inc(S,f[i-1][j]);
			inc(f[i][j],S);
		  }
	  }
	cout<<ans;
	return 0;
}

Submission Info

Judge Result