求最多能有多少个点位于同一直线上

题目描述
对于给定的n个位于同一二维平面上的点，求最多能有多少个点位于同一直线上
Given n points on a 2D plane, find the maximum number of points that lie on the same straight line.

/**
 * 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) {
        int len = points.length;
        if(len < 2)
            return len;
        int max_points = 0;
        for(int i = 0; i < len; i++){
            int dup = 0, vlt = 0;  //重合个数，垂直个数
            Point a = points[i];
            Map<Float,Integer> map = new HashMap<>();   //key为斜率
            for(int j = 0; j < len; j++){
                if(i == j) continue;
                else{
                    Point b = points[j];
                    if(a.x == b.x){
                        if(a.y == b.y) dup++;
                        else vlt++;
                    }
                    else{
                        float k = (float)(b.y - a.y)/(b.x - a.x);
                        if(map.get(k) == null) map.put(k, 1);
                        else map.put(k, 1 + map.get(k));
                    }
                }
            }
            int max = vlt;
            for(float k :map.keySet()){
                max = Math.max(max, map.get(k));
            }
            max_points = Math.max(max_points, max + dup);   //加上重复点的个数
        }
        return max_points + 1;
    }
}