https://oj.leetcode.com/problems/max-points-on-a-line/
http://blog.csdn.net/linhuanmars/article/details/21060933
/**
* 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 {
public int maxPoints(Point[] points) {
{
if (points == null || points.length == 0)
return 0;
int max = 1;
for (int i = 0 ; i < points.length - 1 ; i ++)
{
// 对于该点，使用一个map保存其余点的斜率
Map<Double, Integer> map = new HashMap<>();
int samepoints = 0; // Number of same point.
int x0 = 1; // Number of points with ratio +oo
for (int j = i + 1 ; j < points.length ; j ++)
{
if (points[i].x == points[j].x && points[i].y == points[j].y)
samepoints ++;
else if (points[j].x == points[i].x)
x0 ++;
else
{
// 需要特意比对 ratio 为0 的情况是因为double 有 +0.0d 和 -0.0d
double ratio = (points[i]. y == points[j].y) ?
0d :
(double)(points[j].y - points[i].y) / (double)(points[j].x - points[i].x);
Integer count = map.get(ratio);
if (count == null) count = 1;
count ++;
map.put(ratio, count);
}
}
max = Math.max(max, x0 + samepoints);
for (int count : map.values())
max = Math.max(max, count + samepoints);
}
return max;
}
}
