# 2022-05-18

## 344. Reverse String

### Description

Write a function that reverses a string. The input string is given as an array of characters `s`.

You must do this by modifying the input array in-place with `O(1)` extra memory.

Example 1:

``````Input: s = ["h","e","l","l","o"]
Output: ["o","l","l","e","h"]``````

Example 2:

``````Input: s = ["H","a","n","n","a","h"]
Output: ["h","a","n","n","a","H"]``````

Constraints:

### Solution

``````func reverseString(s []byte) {
for i, j := 0, len(s)-1; i < j; {
s[i], s[j] = s[j], s[i]
i++
j--
}
}``````

## 557. Reverse Words in a String III

### Description

Given a string `s`, reverse the order of characters in each word within a sentence while still preserving whitespace and initial word order.

Example 1:

``````Input: s = "Let's take LeetCode contest"
Output: "s'teL ekat edoCteeL tsetnoc"``````

Example 2:

``````Input: s = "God Ding"
Output: "doG gniD" ``````

Constraints:

• `1 <= s.length <= 5 * 104`

• `s` contains printable ASCII characters.

• `s` does not contain any leading or trailing spaces.

• There is at least one word in `s`.

• All the words in `s` are separated by a single space.

### Solution

#### Approach #0

``````func reverseWord(s []rune) string {
for i, j := 0, len(s)-1; i < j; {
s[i], s[j] = s[j], s[i]
i++
j--
}
return string(s)
}

func reverseWords(s string) string {
sList := strings.Split(s, " ")
var res []string
for _, aS := range sList {
res = append(res, reverseWord([]rune(aS)))
}
return strings.Join(res, " ")
}``````

#### Approach #1

``````func reverseWord(s []rune) {
for i, j := 0, len(s)-1; i < j; {
s[i], s[j] = s[j], s[i]
i++
j--
}
}

func reverseWords(s string) string {
r := []rune(s)
l := 0
for i, letter := range r {
if string(letter) == " " {
reverseWord(r[l:i])
l = i + 1
}
}
reverseWord(r[l:])
return string(r)
}``````

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