Question

给定2D平面上的n个点，找到位于同一直线上的最大点数。

此编程难题取自Leetcode上的here

以下是我尝试解决它。

   /**
     * 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.length==0) return 0;
            Map[] maps = new Map[points.length];
            for (int i=0; i<points.length; i++) {
                Map<Double, Integer> map = new HashMap<Double, Integer>();
                maps[i] = map;
            }
            //count the points with the same coordinates
            int [] identical = new int[points.length];

            //count the points that form a vertical line against the x-axis
            int [] vertical = new int[points.length];
            for (int i=0; i<points.length; i++) {
                for (int j=i+1; j<points.length; j++) {
                    Point A = points[i];
                    Point B = points[j];
                    if (A.x != B.x) {
                        double slope = (A.y-B.y)/(A.x-B.x);
                        if (maps[i].containsKey(slope)) {
                            maps[i].put(slope, (int)maps[i].get(slope)+1);
                        } else {
                            maps[i].put(slope, 1);
                        }
                        if (maps[j].containsKey(slope)) {
                            maps[j].put(slope, (int)maps[j].get(slope)+1);
                        } else {
                            maps[j].put(slope, 1);
                        }
                    } else if (A.y == B.y) {
                        identical[i]++;
                        identical[j]++;
                    } else {
                        vertical[i]++;
                        vertical[j]++;
                    }
                }
            }
            int max = 0;
            for (int i=0; i<points.length; i++) {
                int maxForCurrentPoint = vertical[i];
                for (Object entry : maps[i].entrySet())
                {
                    int num = (int)((Map.Entry)entry).getValue();
                    if (num > maxForCurrentPoint) {
                        maxForCurrentPoint = num;
                    }
                }
                maxForCurrentPoint += identical[i]+1; //the extra 1 counts for the point itself
                if (maxForCurrentPoint > max)
                max = maxForCurrentPoint;
            }
            return max;
        }
    }

但是，我无法通过测试用例。测试结果如下：

19/27测试用例通过。

输入：[[84,250]，[0,0]，[1,0]，[0，-70]，[0，-70]，[1，-1]，[21,10]，[ 42,90]，[ - 42，-230]]   输出：8预期：6

我的代码的逻辑对我来说似乎没问题，但也许我错过了一些我不知道的东西？我也怀疑哈希表的用法。有人可以对这个问题有所了解吗？

Answer 1

该行

double slope = (A.y-B.y)/(A.x-B.x);

错了。这会进行int除法，然后将结果转换为double。你想要

double slope = (A.y-B.y)/(double)(A.x-B.x);

找到位于同一直线上的最大点数

1 个答案: