POJ1118解题报告

  

Lining Up

Time Limit: 2000MS		Memory Limit: 32768K
Total Submissions: 16578		Accepted: 5226

Description

"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!

Input

Input consist several case,First line of the each case is an integer N ( 1 < N < 700 ),then follow N pairs of integers. Each pair of integers is separated by one blank and ended by a new-line character. The input ended by N=0.

Output

output one integer for each input case ,representing the largest number of points that all lie on one line.

Sample Input

5
1 1
2 2
3 3
9 10
10 11
0

Sample Output

3

判断各个点是否在一条直线上，即首先确立两个点，然后判断其他点与这两个点是否是在一条直线上。
import java.util.*;
import javax.swing.RowFilter.Entry;
import java.util.Map.*;
public class Main{
	
	private int len=700;
	private int[] x=new int[len];
	private int[] y=new int[len];
	private int maxnum=0;
	private int num=0;
	
	public void init()
	{
		maxnum=0;
		for(int i=0;i<700;i++)
		{
			x[i]=0;
			y[i]=0;
		}
	}
	public void cal()
	{
		for(int i=0;i<num;i++)
		{
			for(int j=i+1;j<num;j++)
			{
				int temp=0;
				for(int k=j+1;k<num;k++)
				{
					if((y[k]-y[i])*(x[j]-x[i])==(y[j]-y[i])*(x[k]-x[i]))
					{
						temp++;
					}
				}
				if(maxnum<temp)
				{
					maxnum=temp;
				}
			}
		}
		System.out.println(maxnum+2);
	}
	public Main()
	{
		Scanner scan=new Scanner(System.in);
		
		num=scan.nextInt();
		while(num!=0)
		{
			init();
			
			for(int i=0;i<num;i++)
			{
				x[i]=scan.nextInt();
				y[i]=scan.nextInt();
			}
			
			cal();
			num=scan.nextInt();
		}
	}
	public static void main(String[] args)
	{
		Main mainf=new Main();
	}
}