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790. Domino and Tromino Tiling

Difficulty Topics

Description

You have two types of tiles: a 2 x 1 domino shape and a tromino shape. You may rotate these shapes.

Given an integer n, return the number of ways to tile an 2 x n board. Since the answer may be very large, return it modulo 109 + 7.

In a tiling, every square must be covered by a tile. Two tilings are different if and only if there are two 4-directionally adjacent cells on the board such that exactly one of the tilings has both squares occupied by a tile.

 

Example 1:

Input: n = 3
Output: 5
Explanation: The five different ways are show above.

Example 2:

Input: n = 1
Output: 1

 

Constraints:

  • 1 <= n <= 1000

Solution

domino-and-tromino-tiling.py
class Solution:
    def numTilings(self, N):
        a, b, c = 0, 1, 1

        for i in range(N - 1): 
            a, b, c = b, c, (c + c + a) % (10 ** 9 + 7)

        return c