leetcode--max-points-on-a-line_穷举 max-points-on-a-line java-优快云博客

本文介绍了一种算法，用于找出二维平面上给定点集中位于同一直线上的最大点数。通过计算不同点之间的斜率并使用哈希映射进行计数，该算法能有效地解决此几何问题。

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描述

Given n points on a 2D plane, find the maximum number of points that lie on the same straight line.

代码

/**
 * Definition for a point.
 * class Point {
 *     int x;
 *     int y;
 *     Point() { x = 0; y = 0; }
 *     Point(int a, int b) { x = a; y = b; }
 * }
 */
import java.util.*;
public class Solution {
    public int maxPoints(Point[] points) {
        if(points.length==0){
            return 0;
        }
        if(points.length==1){
            return 1;
        }
        int max=0;
        for(int i=0;i<points.length;i++){
            Map<Double,Integer> map=new HashMap<>();
            Map<Point,Integer> exi=new HashMap<>();
            exi.put(points[i],1);
            for(int j=0;j<points.length;j++){
                if(i!=j){
                    Integer temp=exi.get(points[j]);
                    if(points[i].y==points[j].y&&points[i].x==points[j].x){
                        Integer count=exi.get(points[i]);
                        exi.put(points[i],count+1);
                        if(exi.get(points[i])>max){
                            max=exi.get(points[i]);
                        }
                    }else{
                        double k=(double)(points[i].y-points[j].y)/(points[i].x-points[j].x);
                        if(map.get(k)==null){
                            if(exi.get(points[i])!=null){
                                map.put(k,1+exi.get(points[i]));
                            }else{
                                map.put(k,2);
                            }
                        }else{
                            int v=map.get(k);
                            map.put(k,++v);
                        }
                        if(map.get(k)>max){
                            max=map.get(k);
                        }
                    }

                }
            }
        }
        return max;
    }
}