LeetCode | Reverse Words in a String（字符串中的单词序反转）

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.

题目解析：

题目中要删除多余的空格，有一种比较简单的方法，先将s字符串赋给一个临时字符串tmp，将头尾空格略去，两个字间的空格只复制一次。然后对tmp进行常规操作。这样需要两遍遍历。

也可以临时设一个结果字符串，和一个临时的字串。一点一点处理

class Solution {public:    void reverseWords(string &s) {        string tmp;        for(int i = s.size()-1;i >= 0;i--){            while(i >= 0 && s[i] == ' ')                i--;            if(i<0)                break;            if(!tmp.empty())                tmp.push_back(' ');            string word;            while(i>=0 && s[i]!=' ')                word.push_back(s[i--]);            reverse(word.begin(),word.end());            tmp.append(word);        }        s = tmp;    }};