bulb-switcher-ii.py

# Time:  O(1)
# Space: O(1)

# 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:
#   1. Flip all the lights.
#   3. Flip lights with even numbers.
#   3. Flip lights with odd numbers.
#   4. 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].
    
class Solution(object):
    def flipLights(self, n, m):
        """
        :type n: int
        :type m: int
        :rtype: int
        """
        if m == 0:            return 1
        if n == 1:            return 2
        if m == 1 and n == 2: return 3
        if m == 1 or  n == 2: return 4
        if m == 2:            return 7
        return 8