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November 29, 2021 22:00
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reverse the prefix in a word, leetcode #2000 https://leetcode.com/problems/reverse-prefix-of-word/
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/* | |
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] | |
} | |
} |
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