Reverse Words in a String III
(#557), Easy
Category: String, Two Pointer
Problem Statement
Given a string s, reverse the order of characters in each word within a sentence while still preserving whitespace and initial word order.
Examples
Input: s = "Mr Ding"
Output: "rM gniD"
Explanation: Each word is reversed but the order of the words remains the same.
Input: s = "Hello World"
Output: "olleH dlroW"
Explanation: Each word is reversed in place.
Input: s = "a b c"
Output: "a b c"
Explanation: Single character words remain the same.
Approach
Split and Reverse Each Word
- Split the input string by spaces to isolate words.
- For each word, reverse its characters using a two-pointer approach.
- Use a helper function that converts the word to an array, swaps characters from both ends, and joins it back.
- Join the reversed words using spaces to reconstruct the sentence.
var reverseWords = function(s) {
let chars = s.split(" ");
for (let i = 0; i < chars.length; i++) {
chars[i] = reverseWord(chars[i]);
}
return chars.join(" ");
};
function reverseWord(word) {
let start = 0, end = word.length - 1;
let chars = word.split("");
while (start < end) {
[chars[start], chars[end]] = [chars[end], chars[start]];
start++;
end--;
}
return chars.join("");
}Complexity
Time: O(n)
Space: O(n)