Reaching Points

A move consists of taking a point (x, y) and transforming it to either (x, x+y) or (x+y, y).

Given a starting point (sx, sy) and a target point (tx, ty), return True if and only if a sequence of moves exists to transform the point (sx, sy) to (tx, ty). Otherwise, return False.

Examples:
Input: sx = 1, sy = 1, tx = 3, ty = 5
Output: True
Explanation:
One series of moves that transforms the starting point to the target is:
(1, 1) -> (1, 2)
(1, 2) -> (3, 2)
(3, 2) -> (3, 5)

Input: sx = 1, sy = 1, tx = 2, ty = 2
Output: False

Input: sx = 1, sy = 1, tx = 1, ty = 1
Output: True

分析：因为对于起始点来讲，它后面的x和y值永远是增加的，所以，如果sx > tx 或者 sy > ty，那么明显是不行的。
但是从小到大找好像不好找，可以换种思维，从大往小找。

class Solution {
    public boolean reachingPoints(int sx, int sy, int tx, int ty) {
        if (ty < sy || tx < sx) return false;
        while (tx >= sx && ty >= sy) {
            if (tx > ty) tx %= ty;
            else ty %= tx;
        }
        if (tx == sx) {
            return (ty - sy) % sx == 0;
        }
        if (ty == sy) {
            return (tx - sx) % sy == 0;
        }
        return false;
    }
}