C++ | Leetcode C++题解之第149题直线上最多的点数

题目：

题解：

class Solution {
public:
    int gcd(int a, int b) {
        return b ? gcd(b, a % b) : a;
    }

    int maxPoints(vector<vector<int>>& points) {
        int n = points.size();
        if (n <= 2) {
            return n;
        }
        int ret = 0;
        for (int i = 0; i < n; i++) {
            if (ret >= n - i || ret > n / 2) {
                break;
            }
            unordered_map<int, int> mp;
            for (int j = i + 1; j < n; j++) {
                int x = points[i][0] - points[j][0];
                int y = points[i][1] - points[j][1];
                if (x == 0) {
                    y = 1;
                } else if (y == 0) {
                    x = 1;
                } else {
                    if (y < 0) {
                        x = -x;
                        y = -y;
                    }
                    int gcdXY = gcd(abs(x), abs(y));
                    x /= gcdXY, y /= gcdXY;
                }
                mp[y + x * 20001]++;
            }
            int maxn = 0;
            for (auto& [_, num] : mp) {
                maxn = max(maxn, num + 1);
            }
            ret = max(ret, maxn);
        }
        return ret;
    }
};