Submission #1437841

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Source Code Expand

#include<bits/stdc++.h>
using namespace std;
const long long md=1e9+7;
long long n,a,b,x[100005],dp[100005][2];
vector<long long>g1,g2;
int main()
{
	cin>>n>>a>>b;
	x[1]=-(1LL<<62);
	x[n+2]=(1LL<<62);
	g1.push_back(2);
	g2.push_back(2);
	for(int i=2;i<=n+1;i++)
	{
		cin>>x[i];
		if(x[i]-x[i-1]<a)g1.push_back(i);
		if(x[i]-x[i-1]<b)g2.push_back(i);
	}
	dp[1][0]=1;
	dp[1][1]=1;
	for(int i=2;i<=n+1;i++)
	{
		int p1=upper_bound(x,x+n+3,x[i+1]-a)-x-1;
		if(p1==i)p1--;
		int p2=upper_bound(g2.begin(),g2.end(),i)-g2.begin()-1;
		p2=g2[p2]-1;
		if(p1>=p2)dp[i][0]=(dp[p1][1]-dp[p2-1][1]+md)%md;
		dp[i][0]=(dp[i][0]+dp[i-1][0])%md;
		p1=upper_bound(x,x+n+3,x[i+1]-b)-x-1;
		if(p1==i)p1--;
		p2=upper_bound(g1.begin(),g1.end(),i)-g1.begin()-1;
		p2=g1[p2]-1;
		if(p1>=p2)dp[i][1]=(dp[p1][0]-dp[p2-1][0]+md)%md;
		dp[i][1]=(dp[i][1]+dp[i-1][1])%md;
	}
	cout<<(dp[n+1][0]+dp[n+1][1]-dp[n][0]-dp[n][1]+md*2)%md<<endl;
	return 0;
}

Submission Info

Judge Result