Solution2.py

class Solution:
    def checkRecord(self, n: int) -> int:
        mod = int(1e9 + 7)
        dp = [[[0, 0, 0], [0, 0, 0]] for _ in range(n)]

        # base case
        dp[0][0][0] = dp[0][0][1] = dp[0][1][0] = 1

        for i in range(1, n):
            # A
            dp[i][1][0] = (dp[i - 1][0][0] + dp[i - 1][0][1] + dp[i - 1][0][2]) % mod
            # L
            dp[i][0][1] = dp[i - 1][0][0]
            dp[i][0][2] = dp[i - 1][0][1]
            dp[i][1][1] = dp[i - 1][1][0]
            dp[i][1][2] = dp[i - 1][1][1]
            # P
            dp[i][0][0] = (dp[i - 1][0][0] + dp[i - 1][0][1] + dp[i - 1][0][2]) % mod
            dp[i][1][0] = (
                dp[i][1][0] + dp[i - 1][1][0] + dp[i - 1][1][1] + dp[i - 1][1][2]
            ) % mod

        ans = 0
        for j in range(2):
            for k in range(3):
                ans = (ans + dp[n - 1][j][k]) % mod
        return ans