There is a room with n lights which are turned on initially and 4 buttons on the wall. After performing exactly m unknown operations towards buttons, you need to return how many different kinds of status of the n lights could be.
Suppose n lights are labeled as number [1, 2, 3 ..., n], function of these 4 buttons are given below:
- Flip all the lights.
- Flip lights with even numbers.
- Flip lights with odd numbers.
- Flip lights with (3k + 1) numbers, k = 0, 1, 2, ...
Example 1:
Input: n = 1, m = 1.
Output: 2
Explanation: Status can be: [on], [off]
Example 2:
Input: n = 2, m = 1.
Output: 3
Explanation: Status can be: [on, off], [off, on], [off, off]
Example 3:
Input: n = 3, m = 1.
Output: 4
Explanation: Status can be: [off, on, off], [on, off, on], [off, off, off], [off, on, on].
Note: n and m both fit in range [0, 1000].
Runtime: 4 ms, faster than 29.00% of C++ online submissions for Bulb Switcher II.
找规律题。
class Solution {
public:
int flipLights(int n, int m) {
if(m == 0) return 1;
if(n == 1) return 2;
if(n == 2 && m == 1) return 3;
if(n == 2) return 4;
if(m==1) return 4;
if(m == 2) return 7;
return 8;
}
};