Submission #1869437

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Source Code Expand

#include <iostream>
#include <algorithm>
#include<cmath>
#include<cstring>
#include<cstdio>
#include<cstdlib>
#include<vector>
#include<iomanip>
#define sqr(x) (x)*(x)
using namespace std;
long long n,m,i,j,dp[3005][3005],l[3005],r[3005],mod=1000000007,cnt[3005],x,y;
string st;
int main()
{
	cin>>n>>m>>st;
	st=" "+st;
	for (i=1;i<=n;i++) 
	{
		cnt[i]=cnt[i-1]+st[i]-'0';
	}
	for (i=1;i<=n;i++)
	{
		l[i]=i;
		r[i]=i;
	}
	for (i=1;i<=m;i++)
	{
		cin>>x>>y;
		r[x]=max(r[x],y);
	}
	for (i=1;i<=n;i++)
	{
		r[i]=max(r[i],r[i-1]);
	}
	dp[0][0]=1;
	for (i=1;i<=n;i++)
	{
		for (j=0;j<=r[i];j++)
		{
			if (j>cnt[r[i]]) break;
			if (j>=cnt[r[i]]-r[i]+i)
			{
				dp[i][j]=dp[i-1][j]+dp[i-1][j-1];
				dp[i][j]%+mod;
			}
		}
	}
	cout<<dp[n][cnt[n]];
	return 0;
}

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