We have two types of tiles: a 2x1 domino shape, and an "L" tromino shape. These shapes may be rotated.
XX <- domino XX <- "L" tromino X
n, how many ways are there to tile a
2 x n board? Return your answer 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: Input: n = 3 Output: 5 Explanation: The five different ways are listed below, different letters indicates different tiles: XYZ XXZ XYY XXY XYY XYZ YYZ XZZ XYY XXY
nwill be in range