557. Reverse Words in a String III

中文文档

Description

Given a string s, reverse the order of characters in each word within a sentence while still preserving whitespace and initial word order.

 

Example 1:

Input: s = "Let's take LeetCode contest"
Output: "s'teL ekat edoCteeL tsetnoc"

Example 2:

Input: s = "Mr Ding"
Output: "rM gniD"

 

Constraints:

• 1 <= s.length <= 5 * 104
• s contains printable ASCII characters.
• s does not contain any leading or trailing spaces.
• There is at least one word in s.
• All the words in s are separated by a single space.

Solutions

Solution 1: Simulation

We can split the string $\textit{s}$ into an array of words $\textit{words}$ by spaces, then reverse each word and concatenate them back into a string.

The time complexity is $O(n)$, and the space complexity is $O(n)$. Here, $n$ is the length of the string $\textit{s}$.

Python3

class Solution:
    def reverseWords(self, s: str) -> str:
        return " ".join(t[::-1] for t in s.split())

Java

class Solution {
    public String reverseWords(String s) {
        String[] words = s.split(" ");
        for (int i = 0; i < words.length; ++i) {
            words[i] = new StringBuilder(words[i]).reverse().toString();
        }
        return String.join(" ", words);
    }
}

C++

class Solution {
public:
    string reverseWords(string s) {
        stringstream ss(s);
        string t;
        string ans;
        while (ss >> t) {
            reverse(t.begin(), t.end());
            ans += t;
            ans.push_back(' ');
        }
        ans.pop_back();
        return ans;
    }
};

Go

func reverseWords(s string) string {
	words := strings.Fields(s)
	for i, w := range words {
		t := []byte(w)
		slices.Reverse(t)
		words[i] = string(t)
	}
	return strings.Join(words, " ")
}

TypeScript

function reverseWords(s: string): string {
    return s
        .split(' ')
        .map(t => t.split('').reverse().join(''))
        .join(' ');
}

Rust

impl Solution {
    pub fn reverse_words(s: String) -> String {
        s.split(' ')
            .map(|s| s.chars().rev().collect::<String>())
            .collect::<Vec<_>>()
            .join(" ")
    }
}

JavaScript

/**
 * @param {string} s
 * @return {string}
 */
var reverseWords = function (s) {
    return s
        .split(' ')
        .map(t => t.split('').reverse().join(''))
        .join(' ');
};

PHP

class Solution {
    /**
     * @param String $s
     * @return String
     */
    function reverseWords($s) {
        $words = explode(' ', $s);
        foreach ($words as $i => $word) {
            $words[$i] = strrev($word);
        }
        return implode(' ', $words);
    }
}