Leetcode 第151题 最新题解 Reverse Words in a String

Reverse Words in a String

 Total Accepted: 67 Total Submissions: 412My Submissions

Given an input string, reverse the string word by word.

For example,
Given s = "the sky is blue",
return "blue is sky the".

click to show clarification.

Clarification:

• What constitutes a word?
  A sequence of non-space characters constitutes a word.
• Could the input string contain leading or trailing spaces?
  Yes. However, your reversed string should not contain leading or trailing spaces.
• How about multiple spaces between two words?
  Reduce them to a single space in the reversed string.

Leetcode 很久没有更新题目了。太巧了，今天刚刚说150道题结贴，就出新题了，呵呵。

好吧，第一时间贴上来。

思路：

1 从后往前遍历string

2 保存单词，然后需要逆转，在保存到结果中

注意题目中的clarification，处理好其中的空格。

利用了两个额外string保存中间结果。空间复杂度为O(n).

时间复杂度是O(n)，简单题目：2到3星级

void reverseWords(string &s){string rs;for (int i = s.length()-1; i >= 0; ){while (i >= 0 && s[i] == ' ') i--;if (i < 0) break;if (!rs.empty()) rs.push_back(' ');string t;while (i >= 0 && s[i] != ' ') t.push_back(s[i--]);reverse(t.begin(), t.end());rs.append(t);}s = rs;}