lintcode Max Points on a Line

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

Have you met this question in a real interview? 

Yes

Example

Given 4 points: (1,2), (3,6), (0,0), (1,3).

The maximum number is 3.

Tags 

package tju.cs.bigdata;import java.util.HashSet;import java.util.Set;public class MaxPointsonaLine {    /**     * @param points an array of point     * @return an integer     * </br>ac     */    public int maxPoints(Point[] points) {        // Write your code here        int res = 0;        if(points == null) return res;         // points = delSame(points);        int len = points.length;        if(len < 3) return len;        int samecount = 0;        for(int i = 0 ; i < len; i++){            int tmps = 1;            for(int j = 0; j < len; j++){                if(i == j)continue;                if(points[i].x == points[j].x && points[i].y == points[j].y){                    tmps++;                    continue;                }                int tmpc = 2;                for(int k = 0 ;k < len; k++){                    if(k == i || k == j){                        continue;                    }                    if(isOnLine(points[i] , points[j] , points[k])){                        tmpc++;                    }                    }                                if(tmpc > res)res = tmpc;            }            if(tmps > samecount)samecount = tmps;        }                return Math.max(samecount,res);    }   /**     * @param points an array of point     * @return an integer     * 思路錯誤     */    public int maxPoints1(Point[] points) {        // Write your code here        int res = 0;        if(points == null) return res;        int len = points.length;        if(len < 3) return len;        for(int i = 0 ; i < len-1; i++){            int tmpc = 2;            for(int j = 0; j < len; j++){                if(j == i || j == i + 1){                    continue;                }                if(isOnLine(points[i] , points[i+1] , points[j])){                    tmpc++;                }            }            if(tmpc > res)res = tmpc;        }                return res;    }        public boolean isOnLine(Point a, Point b, Point c){        int left = (a.x - b.x)*(c.y - b.y);        int right = (a.y - b.y)*(c.x - b.x);        if(left == right){            return true;        }else{            return false;        }    }public static void main(String[] args){//String string = "[[0,9],[138,429],[115,359],[115,359],[-30,-102],[230,709],[-150,-686],[-135,-613],[-60,-248],[-161,-481],[207,639],[23,79],[-230,-691],[-115,-341],[92,289],[60,336],[-105,-467],[135,701],[-90,-394],[-184,-551],[150,774]]";String string = "[[0,-12],[5,2],[2,5],[0,-5],[1,5],[2,-2],[5,-4],[3,4],[-2,4],[-1,4],[0,-5],[0,-8],[-2,-1],[0,-11],[0,-9]]";System.out.println(string);String[] stes = string.split("],\\[");int steslen = stes.length; stes[0] = stes[0].substring(2, stes[0].length());stes[steslen - 1] = stes[steslen - 1].substring(0, stes[steslen - 1].length() - 2);Set<Point> setpoints = new HashSet<>();for(int i = 0 ; i < stes.length; i ++){System.out.println(stes[i] + " ");int x = Integer.parseInt(stes[i].split(",")[0]);int y = Integer.parseInt(stes[i].split(",")[1]);setpoints.add(new Point(x,y));}Point[] points = setpoints.toArray(new Point[setpoints.size()]);System.out.println("最大的：" + new MaxPointsonaLine().maxPoints(points));}}