149. 直线上最多的点数

给你一个数组 points ，其中 points[i] = [xi, yi] 表示 X-Y 平面上的一个点。求最多有多少个点在同一条直线上。

来源：力扣（LeetCode）
链接：https://leetcode-cn.com/problems/max-points-on-a-line
著作权归领扣网络所有。商业转载请联系官方授权，非商业转载请注明出处。

import java.util.HashMap;
import java.util.Map;
import java.util.Objects;

class Solution {

    private int gcd(int a, int b) {
        while (b != 0) {
            int t = a % b;
            a = b;
            b = t;
        }
        return a;
    }

    public int maxPoints(int[][] points) {
        if (points == null || points.length == 0 || points[0].length == 0) {
            return 0;
        }

        int ret = 0;

        for (int i = 0; i < points.length; ++i) {
            Map<Line, Integer> map = new HashMap<>();
            int same = 1;
            int max = 0;
            for (int j = i + 1; j < points.length; ++j) {
                if (points[i][0] == points[j][0] && points[i][1] == points[j][1]) {
                    same++;
                } else if (points[i][0] == points[j][0]) {
                    Line line = new Line(0, 1);
                    Integer cnt = map.getOrDefault(line, 0);
                    map.put(line, cnt + 1);
                    max = Math.max(max, cnt + 1);
                } else if (points[i][1] == points[j][1]) {
                    Line line = new Line(1, 0);
                    Integer cnt = map.getOrDefault(line, 0);
                    map.put(line, cnt + 1);
                    max = Math.max(max, cnt + 1);
                } else {
                    int x = points[i][0] - points[j][0];
                    int y = points[i][1] - points[j][1];
                    int gcd = gcd(x, y);
                    Line line = new Line(x / gcd, y / gcd);
                    Integer cnt = map.getOrDefault(line, 0);
                    map.put(line, cnt + 1);
                    max = Math.max(max, cnt + 1);
                }
            }

            ret = Math.max(ret, same + max);
        }


        return ret;
    }
}

class Line {
    int x;
    int y;

    public Line(int x, int y) {
        this.x = x;
        this.y = y;
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;
        Line line = (Line) o;
        return x == line.x &&
                y == line.y;
    }

    @Override
    public int hashCode() {
        return Objects.hash(x, y);
    }
}