Binary TreesBinary Trees36
❯
  1. 1Preorder Traversal of a Binary Tree using Recursion
  2. 2Preorder Traversal of a Binary Tree using Iteration
  3. 3Inorder Traversal of a Binary Tree using Recursion
  4. 4Inorder Traversal of a Binary Tree using Iteration
  5. 5Postorder Traversal of a Binary Tree Using Recursion
  6. 6Postorder Traversal of a Binary Tree using Iteration
  7. 7Level Order Traversal of a Binary Tree using Recursion
  8. 8Level Order Traversal of a Binary Tree using Iteration
  9. 9Reverse Level Order Traversal of a Binary Tree using Iteration
  10. 10Reverse Level Order Traversal of a Binary Tree using Recursion
  11. 11Find Height of a Binary Tree
  12. 12Find Diameter of a Binary Tree
  13. 13Find Mirror of a Binary Tree
  14. 14Left View of a Binary Tree
  15. 15Right View of a Binary Tree
  16. 16Top View of a Binary Tree
  17. 17Bottom View of a Binary Tree
  18. 18Zigzag Traversal of a Binary Tree
  19. 19Check if a Binary Tree is Balanced
  20. 20Diagonal Traversal of a Binary Tree
  21. 21Boundary Traversal of a Binary Tree
  22. 22Construct a Binary Tree from a String with Bracket Representation
  23. 23Convert a Binary Tree into a Doubly Linked List
  24. 24Convert a Binary Tree into a Sum Tree
  25. 25Find Minimum Swaps Required to Convert a Binary Tree into a BST
  26. 26Check if a Binary Tree is a Sum Tree
  27. 27Check if All Leaf Nodes are at the Same Level in a Binary Tree
  28. 28Lowest Common Ancestor (LCA) in a Binary Tree
  29. 29Solve the Tree Isomorphism Problem
  30. 30Check if a Binary Tree Contains Duplicate Subtrees of Size 2 or More
  31. 31Check if Two Binary Trees are Mirror Images
  32. 32Calculate the Sum of Nodes on the Longest Path from Root to Leaf in a Binary Tree
  33. 33Print All Paths in a Binary Tree with a Given Sum
  34. 34Find the Distance Between Two Nodes in a Binary Tree
  35. 35Find the kth Ancestor of a Node in a Binary Tree
  36. 36Find All Duplicate Subtrees in a Binary Tree
GraphsGraphs46
❯
  1. 1Breadth-First Search in Graphs
  2. 2Depth-First Search in Graphs
  3. 3Number of Provinces in an Undirected Graph
  4. 4Connected Components in a Matrix
  5. 5Rotten Oranges Problem - BFS in Matrix
  6. 6Flood Fill Algorithm - Graph Based
  7. 7Detect Cycle in an Undirected Graph using DFS
  8. 8Detect Cycle in an Undirected Graph using BFS
  9. 9Distance of Nearest Cell Having 1 - Grid BFS
  10. 10Surrounded Regions in Matrix using Graph Traversal
  11. 11Number of Enclaves in Grid
  12. 12Word Ladder - Shortest Transformation using Graph
  13. 13Word Ladder II - All Shortest Transformation Sequences
  14. 14Number of Distinct Islands using DFS
  15. 15Check if a Graph is Bipartite using DFS
  16. 16Topological Sort Using DFS
  17. 17Topological Sort using Kahn's Algorithm
  18. 18Cycle Detection in Directed Graph using BFS
  19. 19Course Schedule - Task Ordering with Prerequisites
  20. 20Course Schedule 2 - Task Ordering Using Topological Sort
  21. 21Find Eventual Safe States in a Directed Graph
  22. 22Alien Dictionary Character Order
  23. 23Shortest Path in Undirected Graph with Unit Distance
  24. 24Shortest Path in DAG using Topological Sort
  25. 25Dijkstra's Algorithm Using Set - Shortest Path in Graph
  26. 26Dijkstra’s Algorithm Using Priority Queue
  27. 27Shortest Distance in a Binary Maze using BFS
  28. 28Path With Minimum Effort in Grid using Graphs
  29. 29Cheapest Flights Within K Stops - Graph Problem
  30. 30Number of Ways to Reach Destination in Shortest Time - Graph Problem
  31. 31Minimum Multiplications to Reach End - Graph BFS
  32. 32Bellman-Ford Algorithm for Shortest Paths
  33. 33Floyd Warshall Algorithm for All-Pairs Shortest Path
  34. 34Find the City With the Fewest Reachable Neighbours
  35. 35Minimum Spanning Tree in Graphs
  36. 36Prim's Algorithm for Minimum Spanning Tree
  37. 37Disjoint Set (Union-Find) with Union by Rank and Path Compression
  38. 38Kruskal's Algorithm - Minimum Spanning Tree
  39. 39Minimum Operations to Make Network Connected
  40. 40Most Stones Removed with Same Row or Column
  41. 41Accounts Merge Problem using Disjoint Set Union
  42. 42Number of Islands II - Online Queries using DSU
  43. 43Making a Large Island Using DSU
  44. 44Bridges in Graph using Tarjan's Algorithm
  45. 45Articulation Points in Graphs
  46. 46Strongly Connected Components using Kosaraju's Algorithm

Left Rotate an Array by One Place using Loop - Optimal Algorithm

Arrays

Contents

ProblemExamplesVisualizationSolutionAlgorithmCodeTimeSpace Detailed Exmpl

Problem Statement❯

Given an array of integers, your task is to left rotate the array by 1 position. This means that each element moves one place to the left, and the first element is moved to the end of the array.

The operation should be performed in-place using an optimal solution, without using extra space for a new array.

If the array is empty or contains only one element, it should remain unchanged after rotation.

Examples❯

Input Array Output Array (After 1 Left Rotation) Description
[1, 2, 3, 4, 5] [2, 3, 4, 5, 1] Normal case – first element moved to the endVisualization
[10] [10] Single-element array remains the sameVisualization
[] [] Empty array remains unchangedVisualization
[5, 10, 15] [10, 15, 5] All elements shifted left once, first element placed lastVisualization
[7, 8] [8, 7] Two-element array rotationVisualization
[0, 0, 0] [0, 0, 0] All elements are the same; rotation does not change the appearanceVisualization

Visualization Player

Solution❯

Understanding the Problem

We are given an array, and our goal is to left rotate it by one position. This means that each element in the array should shift one position to the left, and the first element should move to the last position.

Let’s solve this step by step using an example. We'll also think like a beginner, and make sure we handle all the edge cases clearly.

Step-by-Step Example

Original Array:

[1, 2, 3, 4, 5]

Step 1: Save the first element

We store 1 in a temporary variable because it will be moved to the end later.

Step 2: Shift all other elements left

Move each element one step to the left:

[2, 3, 4, 5, _]

Step 3: Place the saved element at the end

Put 1 in the last position:

[2, 3, 4, 5, 1]

Final Result:

[2, 3, 4, 5, 1]

Edge Cases

1. Empty Array

If the array is [], there’s nothing to rotate. We return it as-is.

2. Single Element Array

If the array is [10], rotating it won't change anything since there's only one item.

3. All Elements Identical

If the array is [0, 0, 0], the result looks the same after rotation, but the operation is still performed internally.

Algorithm Steps❯

  1. Given an array arr of size n.
  2. Store the first element in a temporary variable first.
  3. Shift all elements of the array one position to the left (from index 1 to n-1).
  4. Assign first to the last index of the array.
  5. The array is now left-rotated by one place.

Code

Python
JavaScript
Java
C++
C
def left_rotate_by_one(arr):
    if not arr:
        return arr
    first = arr[0]
    for i in range(1, len(arr)):
        arr[i - 1] = arr[i]
    arr[-1] = first
    return arr

# Sample Input
arr = [10, 20, 30, 40, 50]
print("After Left Rotation:", left_rotate_by_one(arr))

Time Complexity❯

CaseTime ComplexityExplanation
Best CaseO(n)Every element (except the first) needs to be shifted one position to the left, which takes linear time regardless of input.
Average CaseO(n)In all scenarios, the array is traversed once to shift elements, resulting in linear time complexity.
Worst CaseO(n)Even in the worst case, each element is moved exactly once, making the operation linear in the number of elements.

Space Complexity❯

O(1)

Explanation: Only one temporary variable is used to store the first element. No additional space is required proportional to input size.

Detailed Step by Step Example❯

Let's left rotate the array by one position.

{ "array": [10,20,30,40,50], "showIndices": true }

Store the first element 10 in a temporary variable.

Shift index 1

Move 20 from index 1 to index 0.

{ "array": [20,20,30,40,50], "showIndices": true, "highlightIndices": [0], "labels": { "0": "updated" } }

Shift index 2

Move 30 from index 2 to index 1.

{ "array": [20,30,30,40,50], "showIndices": true, "highlightIndices": [1], "labels": { "1": "updated" } }

Shift index 3

Move 40 from index 3 to index 2.

{ "array": [20,30,40,40,50], "showIndices": true, "highlightIndices": [2], "labels": { "2": "updated" } }

Shift index 4

Move 50 from index 4 to index 3.

{ "array": [20,30,40,50,50], "showIndices": true, "highlightIndices": [3], "labels": { "3": "updated" } }

Place the first element at the end

Set 10 to index 4.

{ "array": [20,30,40,50,10], "showIndices": true, "highlightIndices": [4], "labels": { "4": "rotated" } }

Final Result:

Array after left rotation: [20, 30, 40, 50, 10]


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