Problem C Andy's First Dictionary（set的使用）

题目链接：Problem C

题意：输入一个文本，找出所有不同的单词，按照字典序从小到大输出，单词不区分大小写。

思路：将字母序列都存为小写，非字母的字符变成空格，然后利用stringstream实现sting对象的自动格式化。

note: 
stringstream对象的使用
#include<sstream>
#include<iostream>
using namespace std;
int main()
{
        string line,word;
        while(getline(cin,line))
        {
                stringstream stream(line);
                cout<<stream.str()<<endl;
                while(stream>>word){cout<<word<<endl;}
        }
        return ;
}
/*
 * input: shanghai no1 school 1989
 * output: shanghi no1 school 1989
 *         shanghai
 *         no1
 *         school
 *         1989
 */

code：

 #include <iostream>
 #include <string>
 #include <set>
 #include <sstream>
 #include <cctype>
 using namespace std;
 set<string> dirt;
 int main()
 {
     string str, word;
     dirt.clear();
     while (cin >> str)
     {
         int len = str.size();
         for (int i = ; i < len; ++i)
         {
             if (isalpha(str[i])) str[i] = tolower(str[i]);
             else str[i] = ' ';
         }
         stringstream buf(str);
         while (buf >> word) dirt.insert(word);
     }
     set<string>::iterator it;
     for (it = dirt.begin(); it != dirt.end(); ++it)
         cout << *it << endl;
     return ;
 }