lintcode(186)最多有多少个点在一条直线上

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Description;

给出二维平面上的n个点，求最多有多少点在同一条直线上。

Explanation:

给出4个点：(1, 2), (3, 6), (0, 0), (1, 3)。

一条直线上的点最多有3个。

Solution:

计算斜率冰雹存在hashmap中，注意 xi ＝ xj 的情况以及两个点相等的情况。

/** * Definition for a point. * class Point { *     int x; *     int y; *     Point() { x = 0; y = 0; } *     Point(int a, int b) { x = a; y = b; } * } */public class Solution {    /**     * @param points an array of point     * @return an integer     */    public int maxPoints(Point[] points) {        // Write your code here        if(points == null || points.length == 0){            return 0;        }        int result = 1;        HashMap<Double , Integer> record = new HashMap<Double , Integer>();        for(int i = 0; i<points.length;i++){            int same = 0;            record.clear();            record.put((double)Integer.MIN_VALUE , 1);            for(int j = i+1;j<points.length;j++){                if(points[j].x == points[i].x && points[j].y == points[i].y){                    same++;                    continue;                }                double k = 0;                if(points[j] == points[i]){                    k = (double)Integer.MAX_VALUE;                }else{                    k = (double)(points[j].y - points[i].y)/(double)(points[j].x - points[i].x);                }                if(record.containsKey(k)){                    record.put(k , record.get(k) + 1);                }else{                    record.put(k , 2);                }            }            for(int count : record.values()){                if(count + same > result){                    result = count + same;                }            }        }        return result;    }}

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