151 Reverse Words in a String 1

Joel Castillo Espinosa 2

DESCRIPTION

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.

Examples

  • 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.

Constraints:

  • 1 ≤ s.length ≤ 3 * $10^4$
  • s contains English letters (upper-case and lower-case), digits, and spaces ’ ’.
  • There is at least one word in s.

SOLUTION 3

word_reverse <- function(s){
  # split by blank space 
  s_split <- strsplit(s, split = " ")
  
  # identify more that one blank space 
  spac<- s_split[[1]] == ""
  s_split_wospac <- s_split[[1]][!spac]
  
  # reverse without blank spaces
  result <- paste(rev(s_split_wospac), collapse = " ")
  return(result)
}

Examples using the function

We can use the examples presented before.

word_reverse("the sky is blue")

## [1] "blue is sky the"

word_reverse( s = "  hello world  ")

## [1] "world hello"

word_reverse( s = "a good   example")

## [1] "example good a"

  1. This problem is originally from LeetCode, you can find it in Leetcode. ↩

  2. Email: jocastillo@colmex.mx. For more content visit my website: https://joelcastillo.netlify.app
    If you have any questions or suggestions, I’d be grateful to hear from you. ↩

  3. This solution is entirely my own work. It was developed using R version 4.4.1 (2024-06-14 ucrt). ↩