Rotate by 2
Input
rotate_queue([1,2,3,4,5], 2)
Output
[3, 4, 5, 1, 2]
Two left rotations move 1 and 2 to the back in order.
Full lesson preview
Rotate a queue by N steps
Rotate the elements of a queue (list) by N steps to the left.
Python practice8 minStacks & QueuesBeginnerLast updated March 27, 2026
Problem statement
Given a list representing the contents of a queue (front at index 0), rotate it left by k steps and return the resulting list. A single left rotation removes the front element and appends it to the back. If k is larger than the queue length, rotation wraps around. Handle empty lists and k values of zero.
Task
Implement rotate_queue(lst, k) that performs k left rotations (front element moves to back) efficiently.
Examples
Input format
Two arguments: a list of values (the queue) and a non-negative integer k.
Output format
A list representing the queue after k left rotations.
Constraints
- 0 <= k
- 0 <= len(lst) <= 10^5 (rotate should handle k larger than len(lst) efficiently)
- Values can be any valid Python objects (tests will use ints).
Samples
Sample 1
Input
rotate_queue([1,2,3], 4)
Output
[2, 3, 1]
4 mod 3 = 1 left rotation -> [2,3,1].