Reverse Words in a String

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.

提交了好多遍，终于成功了，使用了sstream来分割字符串，使用栈来存放分割之后的字符串，然后出栈就是逆序了。。

C++实现代码：

#include<iostream>
#include<string>
#include<sstream>
#include<stack>
using namespace std;

class Solution
{
public:
    void reverseWords(string &s)
    {
        if(s.empty())
            return;
        stringstream ss(s);
        s.clear();
        stack<string> st;
        string tmp;
        while(ss>>tmp)
        {
            st.push(tmp);
        }
        while(!st.empty())
        {
            tmp=st.top();
            st.pop();
            if(!st.empty())
                s+=tmp+' ';
            else
                s+=tmp;
        }
    }
};

int main()
{
    Solution s;
    string ss="  the   sky   is    blue  ";
    cout<<ss.length()<<endl;
    cout<<ss<<endl;
    s.reverseWords(ss);
    cout<<ss.length()<<endl;
    cout<<ss<<endl;
}

运行结果：

运行结果：