Reverse Words in a String

Problem: Given an input string $s$, reverse the order of the words.

A word is defined as a sequence of non-space characters. The words in $s$ will be separated by at least one space.

Return a string of the words in reverse order concatenated by a single space.

Note that $s$ may contain leading or trailing spaces or multiple spaces between two words. The returned string should only have a single space separating the words. Do not include any extra spaces.

Example 1:

Input: s = "the sky is blue"; Output: "blue is sky the"

Example 2:

Input: s = " hello world "; Output: "world hello"

Explanation: Your reversed string should not contain leading or trailing spaces.

Example 3:

Input: s = "a good example"; Output: "example good a"

Explanation: You need to reduce multiple spaces between two words to a single space in the reversed string.

Solution

    def reverseWords(s):
        tempList = list(s.split())
        newStr = ''
        for i in range(len(tempList)-1, -1, -1):
            newStr += tempList[i]
            if i != 0:
                newStr += ' '
        return newStr

Runtime: Since the for loop is iterating over the words in the original string $s$, the runtime is $O(n)$, where $n$ is the number of words in $s$.

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Anusha Murali

Reverse Words in a String

anusha-murali.github.io