790-Domino and Tromino Tiling.md

Author: revanth1718

dsa-solutions/lc-solutions/0700-0799/790-Domino and Tromino Tiling.md

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+---
+id: domino-and-tromino-tiling
+title: Domino and Tromino Tiling
+sidebar_label: Domino and Tromino Tiling
+tags: [Dynamic Programming, Combinatorics, Math, C++, Python, Java]
+description: Solve the problem of finding the number of ways to tile a 2 x n board using 2 x 1 dominos and tromino shapes.
+---
+
+## Problem Statement
+
+### Problem 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 a 2 x `n` board. Since the answer may be very large, return it modulo $10^9 + 7$.
+
+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.
+
+### Examples
+
+**Example 1:**
+```
+Input: n = 3
+Output: 5
+```
+**Explanation:** The five different ways are shown above.
+
+
+### Constraints
+
+- $1 \leq n \leq 1000$
+
+## Solution
+
+### Intuition
+
+To solve this problem, we can use dynamic programming. Let's define `dp[i]` as the number of ways to tile a 2 x `i` board. The recurrence relation can be derived based on the ways we can place the last tile(s) on the board.
+
+### Time Complexity and Space Complexity Analysis
+
+- **Time Complexity**: The solution involves a single loop through the board length `n`, making the time complexity $O(n)$.
+- **Space Complexity**: The space complexity is $O(n)$ to store the dynamic programming array.
+
+### Code
+
+#### C++
+
+```cpp
+class Solution {
+public:
+    int numTilings(int n) {
+        if (n == 1) return 1;
+        if (n == 2) return 2;
+        const int MOD = 1e9 + 7;
+        vector<long> dp(n + 1);
+        dp[0] = 1;
+        dp[1] = 1;
+        dp[2] = 2;
+        for (int i = 3; i <= n; ++i) {
+            dp[i] = (dp[i - 1] + dp[i - 2] + 2 * dp[i - 3]) % MOD;
+        }
+        return dp[n];
+    }
+};
+```
+#### Java
+
+```java
+class Solution {
+    public int numTilings(int n) {
+        if (n == 1) return 1;
+        if (n == 2) return 2;
+        int MOD = 1000000007;
+        long[] dp = new long[n + 1];
+        dp[0] = 1;
+        dp[1] = 1;
+        dp[2] = 2;
+        for (int i = 3; i <= n; ++i) {
+            dp[i] = (dp[i - 1] + dp[i - 2] + 2 * dp[i - 3]) % MOD;
+        }
+        return (int) dp[n];
+    }
+}
+```
+#### Python
+```python
+class Solution:
+    def numTilings(self, n: int) -> int:
+        if n == 1: return 1
+        if n == 2: return 2
+        MOD = 10**9 + 7
+        dp = [0] * (n + 1)
+        dp[0] = 1
+        dp[1] = 1
+        dp[2] = 2
+        for i in range(3, n + 1):
+            dp[i] = (dp[i - 1] + dp[i - 2] + 2 * dp[i - 3]) % MOD
+        return dp[n]
+```