LeetCode-in-Go
151. Reverse Words in a String
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.
Constraints:
1 <= s.length <= 104scontains 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?
Solution
func reverseWords(s string) string {
var result []rune
i := len(s) - 1
for i >= 0 {
if s[i] == ' ' {
i--
continue
}
start := i
for start >= 0 && s[start] != ' ' {
start--
}
if len(result) > 0 {
result = append(result, ' ')
}
result = append(result, []rune(s[start+1:i+1])...)
i = start - 1
}
return string(result)
}