LeetCode:Reverse Words in a String

题目:

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

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

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.

    

解题思路：

       

       从头到尾将每个单词提取出来，反向赋值就行了。由于栈具有“先进后出”的性质，所以我用的栈实现。

class Solution {public:    void reverseWords(string &s) {        stack<string> stk;                istringstream in(s);        string tmp;        while( in >> tmp)            stk.push(tmp);        s = "";        while(!stk.empty())        {            s +=stk.top();            if(stk.size()!=1)                s +=" ";            stk.pop();        }    }};