LeetCode每日一题(858. Mirror Reflection)

There is a special square room with mirrors on each of the four walls. Except for the southwest corner, there are receptors on each of the remaining corners, numbered 0, 1, and 2.

The square room has walls of length p and a laser ray from the southwest corner first meets the east wall at a distance q from the 0th receptor.

Given the two integers p and q, return the number of the receptor that the ray meets first.

The test cases are guaranteed so that the ray will meet a receptor eventually.

Example 1:

Input: p = 2, q = 1
Output: 2

Explanation: The ray meets receptor 2 the first time it gets reflected back to the left wall.

Example 2:

Input: p = 3, q = 1
Output: 1

Constraints:

• 1 <= q <= p <= 1000

---

把房间想象成一个电梯， 电梯的所有 m * p(m 为大于 0 的整数)的高度处左右两边都挂着传感器， 奇数层挂 2 和 1， 偶数层挂 2 和 0，然后这个题就变成了求最小公倍数的题

---

impl Solution {
    
    pub fn mirror_reflection(p: i32, q: i32) -> i32 {
    
        let mut m = 1;
        let mut is_up = true;
        loop {
    
            if p * m % q == 0 {
    
                if p * m / q % 2 == 0 {
    
                    return 2;
                }
                if is_up {
    
                    return 1;
                }
                return 0;
            }
            m += 1;
            is_up = !is_up;
        }
    }
}