2023.09.10 Today's Challenge

https://leetcode.com/problems/count-all-valid-pickup-and-delivery-options/

Count All Valid Pickup and Delivery Options - LeetCode

DP로 푸는 문제.
DP는 언제나 어려운 듯. ㅠ_ㅠ

class Solution:
    def countOrders(self, n: int) -> int:
        MOD = int(1e9 + 7)
        MAX_PAIRS = n + 1
        dp = [0] * MAX_PAIRS
        dp[0] = 1

        for currentPairs in range(1, n + 1):
            dp[currentPairs] = dp[currentPairs - 1] * (2 * currentPairs - 1) * currentPairs % MOD;
        
        return dp[n];