PermutationSequence

Permutation Sequence

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Problem:

The set [1, 2, 3, ..., n] contains a total of n! unique permutations.

By listing and labeling all of the permutations in order, we get the following sequence for n = 3:

1. "123"
2. "132"
3. "213"
4. "231"
5. "312"
6. "321" Given n and k, return the k_th permutation sequence.

Example:

Input: n = 3, k = 3
Output: "213"

Input: n = 4, k = 9
Output: "2314"

Input: n = 3, k = 1
Output: "123"

Note:

• 1 <= n <= 9
• 1 <= k <= n!