Medium Difficulty
Reverse Words in a String


Tow Pointers


Reverse Words in a String

Link to algo

To solve the problem of reversing the order of words in a string, we can split the string into an array of words using the space character as a delimiter. We then reverse the array and join the words back together with a single space separator.

Here's an implementation of the algorithm:

function reverseWords(s) {
  // Remove leading and trailing spaces, and reduce multiple spaces to a single space
  s = s.trim().replace(/\s+/g, " ");
  // Split the string into an array of words
  const words = s.split(" ");
  // Reverse the array of words and join them with a single space separator
  return words.reverse().join(" ");

In this solution, we first remove any leading and trailing spaces from the input string s using the trim method. We then replace any multiple spaces with a single space using a regular expression.

Next, we split the modified string into an array of words using the split method with the space character as the delimiter.

We then reverse the array of words using the reverse method and join them back together into a string using the join method with a single space as the separator.

Finally, we return the resulting reversed string of words.

Here's an example usage of the reverseWords function:

console.log(reverseWords("the sky is blue")); // Output: "blue is sky the"
console.log(reverseWords("  hello world  ")); // Output: "world hello"
console.log(reverseWords("a good   example")); // Output: "example good a"

The time complexity of this algorithm is O(n), where n is the length of the input string s. The operations of trimming, replacing, splitting, reversing, and joining all take linear time.

The space complexity is O(n) as well. The array of words will have a length proportional to the input string length, and the reversed string will also have the same length.