C++14(g++5.4) 解法, 执行用时: 9ms, 内存消耗: 504K, 提交时间: 2020-08-05 11:07:51

#include <iostream>
using namespace std;

struct Node
{
    double x;
    double y;
};

double cross(Node q, Node b, Node c)
{
    return (q.x-b.x)*(c.y-b.y)-(q.y-b.y)*(c.x-b.x);
}

int main()
{
    int t;
    cin >> t;
    while(t--){
        Node a, b, c, d;
        cin >> a.x >> a.y >> b.x >> b.y >> c.x >> c.y >> d.x >> d.y;
        if(cross(a,d,c)*cross(b,d,c)<=0&&cross(c,a,b)*cross(d,a,b)<=0){
            cout << "Yes" << endl;
        }
        else{
            cout << "No" << endl;
        }
    }
}

C++11(clang++ 3.9) 解法, 执行用时: 8ms, 内存消耗: 504K, 提交时间: 2020-02-29 22:44:56

#include<iostream>
using namespace std;
int main()
{
	int t;
	cin>>t;
	int x1,x2,x3,x4,y1,y2,y3,y4;
	while(t--)
	{
		cin>>x1>>y1>>x2>>y2>>x3>>y3>>x4>>y4;
		double t=((y2-y1)*1.0/(x2-x1)*x1-(y4-y3)*1.0/(x4-x3)*x3+y3-y1)/((y2-y1)*1.0/(x2-x1)-(y4-y3)*1.0/(x4-x3));
		if(t>=min(x1,x2)&&t<=max(x1,x2)&&t>=min(x3,x4)&&t<=max(x3,x4)) cout<<"Yes"<<endl;
		else cout<<"No"<<endl;
	}
	return 0;
}