g1301_1400.s1359_count_all_valid_pickup_and_delivery_options

Class Solution

java.lang.Object

g1301_1400.s1359_count_all_valid_pickup_and_delivery_options.Solution

public class Solution
extends Object

1359 - Count All Valid Pickup and Delivery Options.

Hard

Given n orders, each order consist in pickup and delivery services.

Count all valid pickup/delivery possible sequences such that delivery(i) is always after of pickup(i).

Since the answer may be too large, return it modulo 10^9 + 7.

Example 1:

Input: n = 1

Output: 1

Explanation: Unique order (P1, D1), Delivery 1 always is after of Pickup 1.

Example 2:

Input: n = 2

Output: 6

Explanation: All possible orders:

(P1,P2,D1,D2), (P1,P2,D2,D1), (P1,D1,P2,D2), (P2,P1,D1,D2), (P2,P1,D2,D1) and (P2,D2,P1,D1).

This is an invalid order (P1,D2,P2,D1) because Pickup 2 is after of Delivery 2.

Example 3:

Input: n = 3

Output: 90

Constraints:

• 1 <= n <= 500

Constructor Summary

Constructors

Constructor and Description
Solution()

Method Summary

Modifier and Type	Method and Description
int	countOrders(int n)

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

Solution

public Solution()

Method Detail

countOrders

public int countOrders(int n)