Rearrange Words in a Sentence

Intuition

The problem is a direct sorting task once we normalise case. We lowercase the whole sentence so capitalization does not interfere with the final formatting, then split it into words. Sorting the words by length gives the required ascending order, and using a stable sort keeps words of equal length in their original relative positions, which is exactly the tie-breaking rule. After joining the sorted words back together with single spaces, we only need to capitalize the very first character to produce a properly formatted sentence.

Algorithm walkthrough

1. 1Lowercase the entire sentence so the original capital letter no longer matters.
2. 2Split the lowercased text into individual words on the single spaces.
3. 3Stable-sort the words by ascending length so equal-length words keep their original order.
4. 4Join the sorted words back into one string separated by single spaces.
5. 5Uppercase the first character of the joined string and return it.

Implementation

class Solution:
    def arrangeWords(self, text: str) -> str:
        words = text.lower().split()
        words.sort(key=len)
        result = " ".join(words)
        return result[0].upper() + result[1:]