Moderate Recursion Question 139 of 224

How do you generate all permutations of an array of distinct integers?

DSA interview set · Speak this in 60–90 seconds · Faridabad & Delhi NCR

01234

Index starts at 0. Scan once for max — O(n).

Backtrack by swapping the next position with each remaining candidate, or by choosing unused indices with a used array.

Why interviewers care about Recursion:

This is a process

question about Recursion.

Panels listen for order,

trade-offs, and what you would actually do on a DSA project - not buzzwords.

Stay structured

Name the idea, why it exists, then one short example.

Close cleanly

End with when you use it and one common pitfall.

Before you speak the answer, walk the interviewer through these steps:

1
Backtrack by swapping the
next position with each remaining candidate, or by choosing unused indices with a used array.
2
Why it exists
There are n!
3
permutations, so time is
O(n * n!) and stack space is O(n).
4
Duplicate values need extra
skipping rules, a common follow-up.
5
Common mistake
What juniors usually get wrong.
6
Close
When you pick this over the alternative.

Here's a short line you can speak, broken into clear beats:

Say this line

“permutations, so time is O(n * n!) and stack space is O(n).”

Break into beats

permutationssotimeisOn

Speaking order

2987408337471632900

Note: Adapt this scaffold to your own project — keep it under 60–90 seconds.

Backtrack by swapping the next position with each remaining candidate, or by choosing unused indices with a used array. There are n!