LeetCode-in-Java

149. Max Points on a Line

Hard

Given an array of points where points[i] = [xi, yi] represents a point on the X-Y plane, return the maximum number of points that lie on the same straight line.

Example 1:

Input: points = [[1,1],[2,2],[3,3]]

Output: 3

Example 2:

Input: points = [[1,1],[3,2],[5,3],[4,1],[2,3],[1,4]]

Output: 4

Constraints:

• 1 <= points.length <= 300
• points[i].length == 2
• -104 <= xi, yi <= 104
• All the points are unique.

Solution

public class Solution {
    public int maxPoints(int[][] points) {
        if (points.length < 2) {
            return points.length;
        }
        int max = 0;
        for (int i = 0; i < points.length; i++) {
            for (int j = i + 1; j < points.length; j++) {
                int x = points[j][0] - points[i][0];
                int y = points[j][1] - points[i][1];
                int c = x * points[j][1] - y * points[j][0];
                int count = 2;
                for (int k = j + 1; k < points.length; k++) {
                    if (c == x * points[k][1] - y * points[k][0]) {
                        count++;
                    }
                }
                max = Math.max(count, max);
            }
        }
        return max;
    }
}

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