LeetCode in Kotlin
790. Domino and Tromino Tiling
Medium
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
class Solution {
fun numTilings(n: Int): Int {
val result = when (n) {
1 -> 1
2 -> 2
3 -> 5
4 -> 11
5 -> 24
else -> {
val dp = LongArray(n + 1)
dp[0] = 0
dp[1] = 1
dp[2] = 2
dp[3] = 5
dp[4] = 11
dp[5] = 24
dp[6] = 53
for (i in 7..n) {
dp[i] = (dp[i - 1] * 2 + dp[i - 3]) % 1000000007
}
return dp[n].toInt() % 1000000007
}
}
return result
}
}