ReverseWordsInString151.kt

package medium

/**

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.
Example 4:

Input: s = "  Bob    Loves  Alice   "
Output: "Alice Loves Bob"
Example 5:

Input: s = "Alice does not even like bob"
Output: "bob like even not does Alice"


Constraints:

1 <= s.length <= 104
s contains English letters (upper-case and lower-case), digits, and spaces ' '.
There is at least one word in s.


Follow-up: If the string data type is mutable in your language, can you solve it in-place with O(1) extra space?
 */

fun reverseWords(s: String): String {

    val words = s.split(" ").filter {
        it.isNotEmpty()
    }
    val builder = StringBuilder()
    for(i in words.size-1 downTo 0)
        builder.append("${words[i]} ")

    return builder.toString().trim()
}