【Atcoder Beginner Contest 207】C - Many Segments

【Atcoder Beginner Contest 207】C - Many Segments

Time Limit: \(2\) sec / Memory Limit: \(1024\) MB

Score : \(300\) points

Problem Statement

You are given \(N\) intervals numbered \(1\) through \(N\), that are as follows:

• if \(t_i=1\), Interval \(i\) is \([l_i,r_i]\);
• if \(t_i=2\), Interval \(i\) is \([l_i,r_i)\);
• if \(t_i=3\), Interval \(i\) is \((l_i,r_i]\);
• if \(t_i=4\), Interval \(i\) is \((l_i,r_i)\);

How many pairs of integers (i,j) satisfying 1≤i<j≤N are there such that Interval i and Interval j intersect?

Constraints

• \(2≤N≤2000\)
• \(1≤ti≤4\)
• \(1≤l_i<r_i≤10^9\)
• All values in input are integers.

Input

Input is given from Standard Input in the following format:

\(N\)
\(t_1\) \(l_1\) \(r_1\)
\(t_2\) \(l_2\) \(r_2\)
⋮⋮
\(t_N\) \(l_N\) \(r_N\)

Output

Print the number of pairs of integers \((i,j)\) such that Interval \(i\) and Interval \(j\) intersect.

//就一条，这个+-0.5的操作属实惊到我了，我本来还想整个前缀和来着！
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
const int N=3005;
double l[N],r[N];
int main()
{
	int n;
	ll ans=0;
	cin>>n;
	for(int i=1;i<=n;i++)
	{
		int op;
		cin>>op>>l[i]>>r[i];
		if(op==2||op==4)r[i]-=0.5;
		if(op==3||op==4)l[i]+=0.5;
		for(int j=1;j<i;j++)if(l[i]<=r[j]&&l[j]<=r[i])ans++;
	}
	cout<<ans<<endl;
	return 0;
}