Enumerating All Permutations

Using C++ next_permutation:

sort(arr.begin(), arr.end())
do {
    // process current permutation
} while (next_permutation(arr.begin(), arr.end()))

Using Python itertools:

from itertools import permutations
for perm in permutations(arr):
    # process perm

Manual recursion: Use the backtracking template with used array.

Time: $O(n! \cdot n)$. There are $n!$ permutations, each taking $O(n)$ to process.

When feasible: $n \leq 10$ gives $\leq 3.6 \times 10^6$ permutations.