reverse the prefix in a word, leetcode #2000 https://leetcode.com/problems/reverse-prefix-of-word/

reverse_prefix.go

/*
Given a 0-indexed string word and a character ch, reverse the segment of word that starts at index 0 and ends at the index of the first occurrence of ch (inclusive). If the character ch does not exist in word, do nothing.

For example, if word = "abcdefd" and ch = "d", then you should reverse the segment that starts at 0 and ends at 3 (inclusive). The resulting string will be "dcbaefd".
Return the resulting string.

 

Example 1:

Input: word = "abcdefd", ch = "d"
Output: "dcbaefd"
Explanation: The first occurrence of "d" is at index 3. 
Reverse the part of word from 0 to 3 (inclusive), the resulting string is "dcbaefd".
Example 2:

Input: word = "xyxzxe", ch = "z"
Output: "zxyxxe"
Explanation: The first and only occurrence of "z" is at index 3.
Reverse the part of word from 0 to 3 (inclusive), the resulting string is "zxyxxe".
Example 3:

Input: word = "abcd", ch = "z"
Output: "abcd"
Explanation: "z" does not exist in word.
You should not do any reverse operation, the resulting string is "abcd".
 

Constraints:

1 <= word.length <= 250
word consists of lowercase English letters.
ch is a lowercase English letter.
*/
func reversePrefix(word string, ch byte) string {
    char := string([]byte{ch})
    prefixArr := strings.Split(word, char)
    if len(prefixArr) > 1 {
        rns := []rune(prefixArr[0]) // convert to rune
        for i, j := 0, len(rns)-1; i < j; i, j = i+1, j-1 {

            // swap the letters of the string,
            // like first with last and so on.
            rns[i], rns[j] = rns[j], rns[i]
        }

        // return the reversed string.
        var resp string
        for k := 0; k < len(prefixArr) - 1; k++ {
            if k == 0 {
                resp = char + string(rns)
            } else {
                resp = resp + prefixArr[k] + char
            }
        }
        return resp + prefixArr[len(prefixArr)-1]
    } else {
        return prefixArr[0]
    }
}