Count All Valid Pickup and Delivery Options

Given n orders, where each order consists of a pickup and a delivery, count all valid sequences of pickups and deliveries where each delivery occurs after its respective pickup. Return the answer modulo 10^9 + 7.

Constraints

  • 1 <= n <= 500
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class Solution:
def countValidPickupAndDeliveryOptions(self, n: int) -> int:
Console

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