LeetCode – Refresh – Max Points on a Line

Notes:

1. Do not forget to check xi == xj. It will cause INF.

2. DO not forget to initialize the iterator.

/**
 * Definition for a point.
 * struct Point {
 *     int x;
 *     int y;
 *     Point() : x(0), y(0) {}
 *     Point(int a, int b) : x(a), y(b) {}
 * };
 */
class Solution {
public:
    int maxPoints(vector<Point> &points) {
        int len = points.size(), duplicates = 1, result = 0;
        if (len < 3) return len;
        unordered_map<double, int> mapping;
        for (int i = 0; i < points.size(); i++) {
            mapping.clear();
            mapping[INT_MIN] = 0;
            duplicates = 1;
            for (int j = 0; j < len; j++) {
                if (i == j) continue;
                if (points[i].x == points[j].x && points[i].y == points[j].y) {
                    duplicates++;
                    continue;
                }
                if (points[i].x == points[j].x) {
                    mapping[INT_MAX]++;
                    continue;
                }
                double k = double(points[i].y - points[j].y)/(points[i].x - points[j].x);
                mapping[k]++;
            }
            for (unordered_map<double, int>::iterator it = mapping.begin(); it != mapping.end(); it++) {
                result = max(result, it->second + duplicates);
            }
        }
        return result;
    }
};