check-if-point-is-reachable.cpp

// Time:  O(log(min(a, b)))
// Space: O(1)

// number theory
class Solution {
public:
    bool isReachable(int targetX, int targetY) {
        const int g = gcd(targetX, targetY);
        return g == (g & ~(g - 1));  // co-prime other than factor 2
    }
};