Given an input string, reverse the string word by word. A word is defined as a sequence of non-space characters.
The input string does not contain leading or trailing spaces and the words are always separated by a single space.
For example,
Given s = "the sky is blue",
return "blue is sky the".
Could you do it in-place without allocating extra space?
给定输入字符串,逐字反转字符串。单词被定义为非空格字符序列。
输入字符串不包含前导或后缀空格,并且单词总是由一个空格分隔。
例如,
给定 s = "the sky is blue",
返回 "blue is sky the".。
您能在不分配额外空间的情况下就地完成吗?
1 class Solution { 2 func reverseWords(_ s: inout String){ 3 var left:Int = 0 4 for i in 0...s.count 5 { 6 if i == s.count || s[i] == " " 7 { 8 reverse(&s, left, i - 1) 9 left = i + 1 10 } 11 } 12 reverse(&s, 0, s.count - 1) 13 } 14 15 func reverse(_ s: inout String,_ left:Int,_ right) 16 { 17 while (left < right) 18 { 19 var t:Character = s[left] 20 s[left] = s[right] 21 s[right] = t 22 left += 1 23 right -=1 24 } 25 } 26 } 27 28 extension String { 29 //subscript函数可以检索数组中的值 30 //直接按照索引方式截取指定索引的字符 31 subscript (_ i: Int) -> Character { 32 //读取字符 33 get {return self[index(startIndex, offsetBy: i)]} 34 35 //修改字符 36 set 37 { 38 var str:String = self 39 var index = str.index(startIndex, offsetBy: i) 40 str.remove(at: index) 41 str.insert(newValue, at: index) 42 self = str 43 } 44 } 45 }
原文地址:https://www.cnblogs.com/strengthen/p/10172134.html
时间: 2024-07-29 23:26:06