Reverse Words in a String — LeetCode 151 Python Solution

The problem

Given an input string s, reverse the order of the words. A word is defined as a sequence of non-space characters.

Example

Input

s = "the sky is blue"

Output

"blue is sky the"

Python solution

class Solution:
    def reverseWords(self, s: str) -> str:
        words = []
        i, n = 0, len(s)
        while i < n:
            while i < n and s[i] == " ":
                i += 1
            if i < n:
                j = i
                while j < n and s[j] != " ":
                    j += 1
                words.append(s[i:j])
                i = j
        return " ".join(words[::-1])

Complexity

Pattern: Two Pointers

Use the order already in the input to discard half the search space at every step. LeetCode 151. Reverse Words in a String is filed here on both counts: the reference solution below belongs to the algorithm family this hub collects, and LeetCode tags it Two Pointers.

The two pointers guide has the Python template for the pattern and the 201 LeetCode problems that use it.

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