Q75: Permutations. - DSA Patterns (Multi-Lang)

In Simple Words: At each level, pick any unused element from nums (track with a visited set or in-place swapping). Recurse until perm size equals $N$.

Time: $O(N! \cdot N)$ | Space: $O(N)$

Multi-Language SolutionsPython 3 • JavaScript • TypeScript • Java • C++

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def permute(nums: list[int]) -> list[list[int]]:
    res = []
    def backtrack(curr, used):
        if len(curr) == len(nums):
            res.append(curr.copy())
            return
        for n in nums:
            if n not in used:
                used.add(n)
                curr.append(n)
                backtrack(curr, used)
                curr.pop()
                used.remove(n)
    backtrack([], set())
    return res