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1359. Count All Valid Pickup and Delivery Options 👍

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class Solution {
 public:
  int countOrders(int n) {
    constexpr int kMod = 1'000'000'007;
    long ans = 1;

    for (int i = 1; i <= n; ++i)
      ans = ans * i * (i * 2 - 1) % kMod;

    return ans;
  }
};

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class Solution {
  public int countOrders(int n) {
    final int kMod = 1_000_000_007;
    long ans = 1;

    for (int i = 1; i <= n; ++i)
      ans = ans * i * (i * 2 - 1) % kMod;

    return (int) ans;
  }
}

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class Solution:
  def countOrders(self, n: int) -> int:
    kMod = 1_000_000_007
    ans = 1

    for i in range(1, n + 1):
      ans = ans * i * (i * 2 - 1) % kMod

    return ans