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Code Implementation

Array Rotator Implementation

Below is the implementation of the array rotator:

solution.js

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/**
 * Array Reversal Approach
 * Time Complexity: O(n) - We need to reverse the array three times
 * Space Complexity: O(1) - We only use a constant amount of extra space
 *
 * @param {number[]} nums - The array to be rotated
 * @param {number} k - The number of steps to rotate
 * @return {void} Do not return anything, modify nums in-place instead
 */
function rotate(nums, k) {
  const n = nums.length;
  k %= n; // Calculate effective number of rotations
 
  if (n === 1 || k === 0) {
    return; // No rotation needed
  }
 
  // Helper function to reverse a portion of the array
  function reverse(start, end) {
    while (start < end) {
      // Swap elements at start and end indices
      const temp = nums[start];
      nums[start] = nums[end];
      nums[end] = temp;
      start++;
      end--;
    }
  }
 
  // Reverse the entire array
  reverse(0, n - 1);
 
  // Reverse the first k elements
  reverse(0, k - 1);
 
  // Reverse the remaining n-k elements
  reverse(k, n - 1);
}

Step-by-Step Explanation

Let's break down the implementation:

1. Understand the Problem: First, understand that we need to rotate an array to the right by k steps, which means each element should be moved k positions to the right, with elements that go beyond the end of the array wrapping around to the beginning.
2. Calculate Effective Rotations: Calculate the effective number of rotations as k % n, where n is the length of the array, since rotating by n steps brings the array back to its original state.
3. Implement the Array Reversal Approach: Use the array reversal technique to perform the rotation in-place with O(1) extra space.
4. Reverse the Entire Array: First, reverse the entire array to get a partially rotated result.
5. Reverse the First k Elements: Reverse the first k elements to put them in their correct order.
6. Reverse the Remaining Elements: Reverse the remaining n-k elements to complete the rotation.
7. Handle Edge Cases: Consider edge cases such as when the array has only one element or when k is 0 or a multiple of the array length.

Previous Next

String Problems

Palindrome Checker

Determine if a string reads the same forward and backward.

EasyString Manipulation

Message Encryption

Reverse a string to create a simple encryption system.

EasyString Manipulation

Word Puzzle Challenge

Check if two strings are anagrams of each other.

EasyString Manipulation

Learning Objective

Implement the array rotator solution in different programming languages.

Array Rotator Implementation

Below is the implementation of the array rotator in different programming languages. Select a language tab to view the corresponding code.

solution.js

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/**
 * Array Reversal Approach
 * Time Complexity: O(n) - We need to reverse the array three times
 * Space Complexity: O(1) - We only use a constant amount of extra space
 *
 * @param {number[]} nums - The array to be rotated
 * @param {number} k - The number of steps to rotate
 * @return {void} Do not return anything, modify nums in-place instead
 */
function rotate(nums, k) {
  const n = nums.length;
  k %= n; // Calculate effective number of rotations
 
  if (n === 1 || k === 0) {
    return; // No rotation needed
  }
 
  // Helper function to reverse a portion of the array
  function reverse(start, end) {
    while (start < end) {
      // Swap elements at start and end indices
      const temp = nums[start];
      nums[start] = nums[end];
      nums[end] = temp;
      start++;
      end--;
    }
  }
 
  // Reverse the entire array
  reverse(0, n - 1);
 
  // Reverse the first k elements
  reverse(0, k - 1);
 
  // Reverse the remaining n-k elements
  reverse(k, n - 1);
}

Step-by-Step Explanation

11. Understand the Problem

First, understand that we need to rotate an array to the right by k steps, which means each element should be moved k positions to the right, with elements that go beyond the end of the array wrapping around to the beginning.

22. Calculate Effective Rotations

Calculate the effective number of rotations as k % n, where n is the length of the array, since rotating by n steps brings the array back to its original state.

33. Implement the Array Reversal Approach

Use the array reversal technique to perform the rotation in-place with O(1) extra space.

44. Reverse the Entire Array

First, reverse the entire array to get a partially rotated result.

55. Reverse the First k Elements

Reverse the first k elements to put them in their correct order.

66. Reverse the Remaining Elements

Reverse the remaining n-k elements to complete the rotation.

77. Handle Edge Cases

Consider edge cases such as when the array has only one element or when k is 0 or a multiple of the array length.

Language-Specific Notes

javascript

JavaScript allows us to modify the array in-place without returning anything.
The modulo operator (%) is used to calculate the effective number of rotations.
A helper function is used to reverse a portion of the array, which makes the code more readable and maintainable.

python

Python provides two approaches: the in-place reversal approach and a more concise slicing approach.
Python's tuple unpacking (nums[start], nums[end] = nums[end], nums[start]) makes the swap operation clean and readable.
The slicing approach (nums[:] = nums[-k:] + nums[:-k]) is more concise but uses O(n) extra space.

java

Java's implementation uses a separate helper method for the reversal operation, which improves code organization.
The solution includes a main method with test cases to demonstrate the functionality.
Java requires explicit type declarations for variables and method parameters.

cpp

C++ provides two implementations: one using the standard library's std::reverse function and another using manual reversal.
The manual reversal approach uses a lambda function to encapsulate the reversal logic.
C++'s std::swap function is used for the element swapping operation in the manual approach.

Key Takeaways

The array reversal approach is an elegant way to rotate an array in-place with O(1) extra space.
Rotating an array by k steps is equivalent to reversing the entire array, then reversing the first k elements, and finally reversing the remaining n-k elements.
When k is larger than the array length, only k % n rotations are needed, where n is the array length.
The problem can be solved in multiple ways, including using extra space, cyclic replacements, or array reversals.
Understanding the mathematical properties of array rotation helps in developing efficient algorithms.
This problem demonstrates the importance of in-place algorithms for optimizing space complexity.

Try It Yourself

Modify the code to implement an alternative approach and test it with the same examples.

Challenge:

Implement a function that solves the array rotator problem using a different approach than shown above.

Common Edge Cases

k = 0

If k is 0, no rotation is needed.

rotate([1, 2, 3, 4, 5], 0) → [1, 2, 3, 4, 5]

k = n

If k is equal to the length of the array, the array remains unchanged.

rotate([1, 2, 3, 4, 5], 5) → [1, 2, 3, 4, 5]

k > n

If k is greater than the length of the array, we only need to perform k % n rotations.

rotate([1, 2, 3, 4, 5], 7) → [4, 5, 1, 2, 3] (equivalent to rotating by 2)

Single Element Array

If the array has only one element, it remains unchanged regardless of k.

rotate([1], 3) → [1]

Empty Array

If the array is empty, it remains empty regardless of k.

rotate([], 3) → []

Solution Approach All Problems

Problem Solution Code

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Array Rotator - Implementation

Code Implementation

Array Rotator Implementation

Below is the implementation of the array rotator:

solution.js

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/**
 * Array Reversal Approach
 * Time Complexity: O(n) - We need to reverse the array three times
 * Space Complexity: O(1) - We only use a constant amount of extra space
 *
 * @param {number[]} nums - The array to be rotated
 * @param {number} k - The number of steps to rotate
 * @return {void} Do not return anything, modify nums in-place instead
 */
function rotate(nums, k) {
  const n = nums.length;
  k %= n; // Calculate effective number of rotations
 
  if (n === 1 || k === 0) {
    return; // No rotation needed
  }
 
  // Helper function to reverse a portion of the array
  function reverse(start, end) {
    while (start < end) {
      // Swap elements at start and end indices
      const temp = nums[start];
      nums[start] = nums[end];
      nums[end] = temp;
      start++;
      end--;
    }
  }
 
  // Reverse the entire array
  reverse(0, n - 1);
 
  // Reverse the first k elements
  reverse(0, k - 1);
 
  // Reverse the remaining n-k elements
  reverse(k, n - 1);
}

Step-by-Step Explanation

Let's break down the implementation:

1. Understand the Problem: First, understand that we need to rotate an array to the right by k steps, which means each element should be moved k positions to the right, with elements that go beyond the end of the array wrapping around to the beginning.
2. Calculate Effective Rotations: Calculate the effective number of rotations as k % n, where n is the length of the array, since rotating by n steps brings the array back to its original state.
3. Implement the Array Reversal Approach: Use the array reversal technique to perform the rotation in-place with O(1) extra space.
4. Reverse the Entire Array: First, reverse the entire array to get a partially rotated result.
5. Reverse the First k Elements: Reverse the first k elements to put them in their correct order.
6. Reverse the Remaining Elements: Reverse the remaining n-k elements to complete the rotation.
7. Handle Edge Cases: Consider edge cases such as when the array has only one element or when k is 0 or a multiple of the array length.

Previous Next

String Problems

Palindrome Checker

Determine if a string reads the same forward and backward.

EasyString Manipulation

Message Encryption

Reverse a string to create a simple encryption system.

EasyString Manipulation

Word Puzzle Challenge

Check if two strings are anagrams of each other.

EasyString Manipulation

Learning Objective

Implement the array rotator solution in different programming languages.

Array Rotator Implementation

Below is the implementation of the array rotator in different programming languages. Select a language tab to view the corresponding code.

solution.js

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/**
 * Array Reversal Approach
 * Time Complexity: O(n) - We need to reverse the array three times
 * Space Complexity: O(1) - We only use a constant amount of extra space
 *
 * @param {number[]} nums - The array to be rotated
 * @param {number} k - The number of steps to rotate
 * @return {void} Do not return anything, modify nums in-place instead
 */
function rotate(nums, k) {
  const n = nums.length;
  k %= n; // Calculate effective number of rotations
 
  if (n === 1 || k === 0) {
    return; // No rotation needed
  }
 
  // Helper function to reverse a portion of the array
  function reverse(start, end) {
    while (start < end) {
      // Swap elements at start and end indices
      const temp = nums[start];
      nums[start] = nums[end];
      nums[end] = temp;
      start++;
      end--;
    }
  }
 
  // Reverse the entire array
  reverse(0, n - 1);
 
  // Reverse the first k elements
  reverse(0, k - 1);
 
  // Reverse the remaining n-k elements
  reverse(k, n - 1);
}

Step-by-Step Explanation

11. Understand the Problem

22. Calculate Effective Rotations

Calculate the effective number of rotations as k % n, where n is the length of the array, since rotating by n steps brings the array back to its original state.

33. Implement the Array Reversal Approach

Use the array reversal technique to perform the rotation in-place with O(1) extra space.

44. Reverse the Entire Array

First, reverse the entire array to get a partially rotated result.

55. Reverse the First k Elements

Reverse the first k elements to put them in their correct order.

66. Reverse the Remaining Elements

Reverse the remaining n-k elements to complete the rotation.

77. Handle Edge Cases

Consider edge cases such as when the array has only one element or when k is 0 or a multiple of the array length.

Language-Specific Notes

javascript

JavaScript allows us to modify the array in-place without returning anything.
The modulo operator (%) is used to calculate the effective number of rotations.
A helper function is used to reverse a portion of the array, which makes the code more readable and maintainable.

python

Python provides two approaches: the in-place reversal approach and a more concise slicing approach.
Python's tuple unpacking (nums[start], nums[end] = nums[end], nums[start]) makes the swap operation clean and readable.
The slicing approach (nums[:] = nums[-k:] + nums[:-k]) is more concise but uses O(n) extra space.

java

Java's implementation uses a separate helper method for the reversal operation, which improves code organization.
The solution includes a main method with test cases to demonstrate the functionality.
Java requires explicit type declarations for variables and method parameters.

cpp

C++ provides two implementations: one using the standard library's std::reverse function and another using manual reversal.
The manual reversal approach uses a lambda function to encapsulate the reversal logic.
C++'s std::swap function is used for the element swapping operation in the manual approach.

Key Takeaways

The array reversal approach is an elegant way to rotate an array in-place with O(1) extra space.
Rotating an array by k steps is equivalent to reversing the entire array, then reversing the first k elements, and finally reversing the remaining n-k elements.
When k is larger than the array length, only k % n rotations are needed, where n is the array length.
The problem can be solved in multiple ways, including using extra space, cyclic replacements, or array reversals.
Understanding the mathematical properties of array rotation helps in developing efficient algorithms.
This problem demonstrates the importance of in-place algorithms for optimizing space complexity.

Try It Yourself

Modify the code to implement an alternative approach and test it with the same examples.

Challenge:

Implement a function that solves the array rotator problem using a different approach than shown above.

Common Edge Cases

k = 0

If k is 0, no rotation is needed.

rotate([1, 2, 3, 4, 5], 0) → [1, 2, 3, 4, 5]

k = n

If k is equal to the length of the array, the array remains unchanged.

rotate([1, 2, 3, 4, 5], 5) → [1, 2, 3, 4, 5]

k > n

If k is greater than the length of the array, we only need to perform k % n rotations.

rotate([1, 2, 3, 4, 5], 7) → [4, 5, 1, 2, 3] (equivalent to rotating by 2)

Single Element Array

If the array has only one element, it remains unchanged regardless of k.

rotate([1], 3) → [1]

Empty Array

If the array is empty, it remains empty regardless of k.

rotate([], 3) → []

Solution Approach All Problems

Code Implementation

Array Rotator Implementation

Step-by-Step Explanation

String ProblemsShow All

Palindrome Checker

Message Encryption

Word Puzzle Challenge

Learning Objective

Array Rotator Implementation

Step-by-Step Explanation

11. Understand the Problem

22. Calculate Effective Rotations

33. Implement the Array Reversal Approach

44. Reverse the Entire Array

55. Reverse the First k Elements

66. Reverse the Remaining Elements

77. Handle Edge Cases

Language-Specific Notes

javascript

python

java

cpp

Key Takeaways

Try It Yourself

Challenge:

Common Edge Cases

k = 0

k = n

k > n

Single Element Array

Empty Array

Array Rotator - Implementation

Code Implementation

Array Rotator Implementation

Step-by-Step Explanation

String ProblemsShow All

Palindrome Checker

Message Encryption

Word Puzzle Challenge

Learning Objective

Array Rotator Implementation

Step-by-Step Explanation

11. Understand the Problem

22. Calculate Effective Rotations

33. Implement the Array Reversal Approach

44. Reverse the Entire Array

55. Reverse the First k Elements

66. Reverse the Remaining Elements

77. Handle Edge Cases

Language-Specific Notes

javascript

python

java

cpp

Key Takeaways

Try It Yourself

Challenge:

Common Edge Cases

k = 0

k = n

k > n

Single Element Array

Empty Array

String Problems

String Problems