Array rotation
Detailed guide and Python implementation for the 'Array rotation' problem.
1. Concept Overview
The 'Array rotation' problem is a key challenge in the Arrays section.
This implementation focuses on easy-level logic in Python.
We prioritize technical accuracy and code readability in our provided solutions.
2. Real-World Applications
3. Visual Intuition
Visualizing the logic flow for Array rotation.
4. Prerequisites
5. Step-by-Step Thinking
1. Understand the problem
Read the problem statement for Array rotation carefully.
2. Formulate brute force
Draft a simple iterative solution.
3. Identify inefficiency
Look for redundant calculations.
4. Optimize search path
Use hashing or sorting to speed up the process.
5. Final Implementation
Clean up the code for production standards.
Problem Statement
Write a function rotate_array(arr, k) that rotates the array arr to the left by k positions and returns the rotated array. Elements that go past the beginning wrap around to the end. For example, rotating [1,2,3,4,5] left by 2 gives [3,4,5,1,2].
- •0 <= len(arr) <= 10^5
- •0 <= k <= 10^6
- •-10^9 <= arr[i] <= 10^9
Examples
arr = [1, 2, 3, 4, 5], k = 2
[3, 4, 5, 1, 2]
Rotate left by 2: first 2 elements [1,2] move to the end.
arr = [10, 20, 30, 40], k = 1
[20, 30, 40, 10]
Rotate left by 1: 10 moves to the end.
arr = [1, 2, 3], k = 3
[1, 2, 3]
Rotating by the array length returns the original array.
Need a Hint?
Edge Cases to Watch
- Empty input structures
- Single element inputs
- Large numerical bounds
Ready to Solve?
Open the problem in PyRun's browser-based Python editor. Your code runs fully offline — no server required.
Interview Insights & Variations
Complexity Analysis Breakdown
Why Time: Directly evaluates all possibilities.
Why Space: Uses standard local memory.
Why Time: Optimized paths reduce total operations.
Why Space: May trade memory for speed.
Optimized Solution Python Code
Optimized Solution Python Code
def rotate_array(arr, d):
# Optimized: Reversal algorithm or slicing
n = len(arr)
if n == 0: return arr
d %= n
# Using slicing for O(n) performance and Pythonic style
return arr[d:] + arr[:d]Brute Force Code (Spoiler Guarded)
Brute Force Code (Spoiler Guarded)
def rotate_array(arr, d):
# Brute force: Rotate one by one d times
n = len(arr)
if n == 0: return arr
d %= n
for _ in range(d):
temp = arr[0]
for i in range(n - 1):
arr[i] = arr[i + 1]
arr[n - 1] = temp
return arrAlgorithm Pattern Checklist
When dealing with Arrays data patterns.
Core Prerequisites
Revision Key Notes
Common Mistakes & Pitfalls
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