LeetCode 4

Max Points on a Line https://oj.leetcode.com/problems/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.

这个题的思路就是找数组里的两个点，用这两个点来做一条直线，然后看数组里的点都在直线上不，我用的是两点式，需要考虑两个点x或y坐标相同的特殊情况。

public class Solution {
    public int maxPoints(Point[] points) {
        int num = points.length;
        int maxPoints = 0;
        if(num == 1) return 1;
        for(int first = 0; first < num; first++){
            for(int second = 0;second < num / 2 +1; second++){
                if(first == second) continue;
                Point firstPoint = points[first];
                Point secondPoint = points[second];
                int count = 0;
                if(firstPoint.x == secondPoint.x){
                    for(int i = 0; i < num; i++){
                        if(points[i].x == firstPoint.x) count++;
                    }
                }else if(firstPoint.y == secondPoint.y){
                    for(int i = 0; i < num; i++){
                        if(points[i].y == firstPoint.y) count++;
                    }
                }else{
                    for(int i = 0; i < num; i++){
                        if((points[i].y - secondPoint.y) * (firstPoint.x - secondPoint.x) == 
                            (firstPoint.y - secondPoint.y) * (points[i].x - secondPoint.x)){
                            count++;
                        }
                    }
                }
                if(count > maxPoints) maxPoints = count;
            }
        }
        return maxPoints;
    }
}