斜率斜率斜率.........

#include<iostream>
#include<cstdio>
#include<algorithm>
#include<map>
#include<cstring>
#include<cstdlib>
#include<vector>
using namespace std;
struct node
{
        int x,y;
        node(){}
        node(int a,int b){x=a;y=b;}
};
int main()
{
       // freopen("in","r",stdin);
        vector<node>box;
        map<double,int>dir;
        string s;
        int T,i,j,k,n,x,y,ans,t;
        cin>>T;
        getchar();
        getchar();
        for(i=0;i<T;i++)
        {
                box.clear();
                if(i)
                        cout<<endl;
                while(1)
                {
                        getline(cin,s);
                        if(s=="\0")
                                break;
                        sscanf(s.c_str(),"%d%d",&x,&y);
                        box.push_back(node(x,y));
                }
                ans=0;
                n=box.size();
                for(j=0;j<n;j++)
                {
                        dir.clear();
                        for(k=j+1;k<n;k++)
                        {
                                t=++dir[double(box[j].y-box[k].y)/double(box[j].x-box[k].x)];
                                ans=max(ans,t);
                        }
                }
                cout<<ans+1<<endl;
        }
        return 0;
}

Lining Up

SubmitStatus

Description

Lining Up

``How am I ever going to solve this problem?

" said the pilot.

Indeed, the pilot was not facing an easy task. She had to drop packages at specific points scattered in a dangerous area. Furthermore, the pilot could only fly over the area once in a straight line, and she had to fly over as many points as possible. All
points were given by means of integer coordinates in a two-dimensional space. The pilot wanted to know the largest number of points from the given set that all lie on one line. Can you write a program that calculates this number?

Your program has to be efficient!

id=21356">Input

The input begins with a single positive integer on a line by itself indicating the number of the cases following, each of them as described below. This line is followed by a blank line, and there is also a blank line between two consecutive inputs.

The input consists of N pairs of integers, where 1 < N < 700. Each pair of integers is separated by one blank and ended by a new-line character. The list of pairs is ended with an end-of-file character. No pair will occur twice.

Output

For each test case, the output must follow the description below. The outputs of two consecutive cases will be separated by a blank line.

The output consists of one integer representing the largest number of points that all lie on one line.

Sample Input

1

1 1
2 2
3 3
9 10
10 11

id=21356">Sample Output

3

Source

Root :: Competitive Programming: Increasing the Lower Bound of Programming Contests (Steven & Felix Halim) :: Chapter 7. (Computational) Geometry :: Geometry Basics ::
Lines

Root :: AOAPC I: Beginning Algorithm Contests (Rujia Liu) :: option=com_onlinejudge&Itemid=8&category=113">
Volume 4. Algorithm Design

Root :: Competitive Programming 3: The New Lower Bound of Programming Contests (Steven & Felix Halim) :: More Advanced Topics :: Problem Decomposition ::
Two Components - Complete Search and Geometry

Root :: Competitive Programming 2: This increases the lower bound of Programming Contests. Again (Steven & Felix Halim) :: (Computational) Geometry :: Basic Geometry ::
Points and Lines