What is the time complexity of permutations?

Worst case O(n × n!). Space complexity is O(n). There are n! outputs, so no algorithm that lists them can be faster.

Permutations

medium

Each position picks one of the remaining values by swapping it forward. Undoing the swap restores the array exactly, so one array serves the entire search instead of n! copies.

Worst O(n × n!)Space O(n)

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Where to go next

Subsets (power set)

medium

One binary decision per element - and a bitmask does the same job.

N-Queens

hard

Switch pruning off and watch the search explode.

Towers of Hanoi

medium

Three lines of recursion, 2ⁿ − 1 provably optimal moves.