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// @Title: 直线上最多的点数 (Max Points on a Line)
// @Author: 15816537946@163.com
// @Date: 2019-09-03 23:33:20
// @Runtime: 8 ms
// @Memory: 3.7 MB
/*
 * @lc app=leetcode.cn id=149 lang=golang
 *
 * [149] 直线上最多的点数
 *
 * https://leetcode-cn.com/problems/max-points-on-a-line/description/
 *
 * algorithms
 * Hard (18.16%)
 * Likes:    71
 * Dislikes: 0
 * Total Accepted:    4.3K
 * Total Submissions: 23.8K
 * Testcase Example:  '[[1,1],[2,2],[3,3]]'
 *
 * 给定一个二维平面，平面上有 n 个点，求最多有多少个点在同一条直线上。
 * 
 * 示例 1:
 * 
 * 输入: [[1,1],[2,2],[3,3]]
 * 输出: 3
 * 解释:
 * ^
 * |
 * |        o
 * |     o
 * |  o  
 * +------------->
 * 0  1  2  3  4
 * 
 * 
 * 示例 2:
 * 
 * 输入: [[1,1],[3,2],[5,3],[4,1],[2,3],[1,4]]
 * 输出: 4
 * 解释:
 * ^
 * |
 * |  o
 * |     o        o
 * |        o
 * |  o        o
 * +------------------->
 * 0  1  2  3  4  5  6
 * 
 */
  
 func maxPoints(points [][]int) int {
	result := 0
	for i, p1 := range points {
		sameP, sameX := 1, 0
		slopeCounts := make(map[float64]int)
		for j := 0; j < i; j++ {
			p2 := points[j]
			if p1[0] == p2[0] && p1[1] == p2[1] {
				sameP++
			} else if p1[0] == p2[0] {
				sameX++
			} else {
				slope := float64(p1[1]-p2[1]) / float64(p1[0]-p2[0])
				if _, exists := slopeCounts[slope]; exists {
					slopeCounts[slope]++
				} else {
					slopeCounts[slope] = 1
				}
			}
		}

		result = int(math.Max(float64(result), float64(sameP+sameX)))
		for _, count := range slopeCounts {
			result = int(math.Max(float64(result), float64(count+sameP)))
		}
	}

	return result
}