day68（1.27）——leetcode面试经典150

149. 直线上最多的点数

149. 直线上最多的点数

题目：

题解：

class Solution {
    public int maxPoints(int[][] points) {
        if(points.length <= 2) {
            return points.length;
        }
        int n=points.length;
        int max_sum = 0;
        for(int i=0;i<points.length;i++) {
            for(int j=i+1;j<points.length;j++) {
                int count = 2;
                int x1 = points[i][0];
                int y1 = points[i][1];
                int x2 = points[j][0];
                int y2 = points[j][1];
                if (x1 == x2) {
                // 垂直线
                    for (int k = 0; k < n; k++) {
                        if (k != i && k != j && points[k][0] == x1) {
                            count++;
                        }
                    }
                } else if (y1 == y2) {
                    // 水平线
                    for (int k = 0; k < n; k++) {
                        if (k != i && k != j && points[k][1] == y1) {
                            count++;
                        }
                    }
                } else {
                    // 斜线
                    double k_val = 1.0 * (y2 - y1) / (x2 - x1);
                    double b_val = y1 - k_val * x1;
                    for (int k = 0; k < n; k++) {
                        if (k != i && k != j) {
                            double y_pred = k_val * points[k][0] + b_val;
                            if (Math.abs(y_pred - points[k][1]) < 1e-6) {
                                count++;
                            }
                        }
                    }
                }
                max_sum = Math.max(max_sum, count);
            }
        }
        return max_sum;
    }
}