How do you solve Rearrange Words in a Sentence on LeetCode?

Rearrange Words in a Sentence (LeetCode #1451) can be solved using Brute Force or Optimal Solution. The optimal approach is Optimal Solution with O(n log n) time complexity and O(n) space complexity. Key insight: Stable sorting maintains the original order of equal elements.

What is the time complexity of Rearrange Words in a Sentence?

The optimal solution for Rearrange Words in a Sentence runs in O(n log n) time and uses O(n) space. The sorting step is O(n log n) due to the stable sort, and we use O(n) space to store the words.

What is the brute force solution for Rearrange Words in a Sentence?

The brute force approach for Rearrange Words in a Sentence is Brute Force, with O(n²) time complexity and O(1) space complexity. The brute force approach involves splitting the sentence into words, sorting them based on their lengths, and then reconstructing the sentence. This method is straightforward but inefficient for larger inputs. The optimal Optimal Solution approach improves this to O(n log n).

What algorithm or data structure is used to solve Rearrange Words in a Sentence?

Rearrange Words in a Sentence uses the following concepts: String, Sorting. The recommended patterns to study are: Sorting, Stable Sort.

What are the interview tips for Rearrange Words in a Sentence?

Always clarify the requirements and constraints of the problem. Discuss your thought process and potential edge cases before coding. Consider time and space complexity during the discussion.

What are common mistakes when solving Rearrange Words in a Sentence?

Not using stable sorting, which can lead to incorrect order for words of the same length. Forgetting to capitalize the first letter of the result.

#1451

Rearrange Words in a Sentence

Medium

StringSortingSortingStable Sort

LeetCode ↗

Approaches

Brute ForceOptimal

Complexity Comparison

	Brute Force	Optimal Solution★
Time	O(n²)	O(n log n)
Space	O(1)	O(n)

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Intuition

Time O(n log n)Space O(n)

The optimal solution leverages a stable sorting algorithm to sort words by length while preserving their original order. This is efficient and handles larger inputs gracefully.

⚙️

Algorithm

3 steps

1Step 1: Split the input text into words.
2Step 2: Use a stable sort to sort the words by their lengths.
3Step 3: Capitalize the first letter of the first word and join the words back into a single string.

solution.py4 lines

1def rearrangeWords(text):
2    words = text.split()
3    words.sort(key=len)
4    return ' '.join(words).capitalize()

ℹ

Complexity note: The sorting step is O(n log n) due to the stable sort, and we use O(n) space to store the words.

1Stable sorting maintains the original order of equal elements.
2Using built-in sort functions can significantly reduce complexity.

Solutions and explanations are original Tejav content. Problem titles © LeetCode — use the LeetCode button above for the full problem statement.