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634. Find the Derangement of An Array

In combinatorial mathematics, a derangement is a permutation of the elements of a set, such that no element appears in its original position.

There's originally an array consisting of n integers from 1 to n in ascending order, you need to find the number of derangement it can generate.

Also, since the answer may be very large, you should return the output mod 109 + 7.

Example 1:

Input: 3
Output: 2
Explanation: The original array is [1,2,3]. The two derangements are [2,3,1] and [3,1,2].

Note:
n is in the range of [1, 106].

Difficulty:

Medium

Lock:

Prime

Company:

Amazon IXL

Problem Solution

634-Find-the-Derangement-of-An-Array

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All contents and pictures on this website come from the Internet and are updated regularly every week. They are for personal study and research only, and should not be used for commercial purposes. Thank you for your cooperation.