Method gcd

149. Max Points on a Line/Solution.cpp:17–30

class Solution {
public:
    int gcd(int a, int b) {
        if ( a < b ) {
            // make a the larger one
            int tmp = b;
            b = a;
            a = tmp;
        }
        while (b != 0) {
            int remaind = a % b;
            a = b;
            b = remaind;
        }
        return a;
    }

    /// how to use 2 integers to represent a double
    /// if 0 -> up = 0, do not represent inf