查找单词的题目，很有意思，我提供了两个版本

//Exercise//9.39://已知有如下 string 对象：string line1 = "We were her pride of 10 she named us:";                                             string line2 = "Benjamin, Phoenix, the Prodigal"                                            string line3 = "and perspicacious pacific Suzanne";                                            string sentence = line1 + ' ' + line2 + ' ' + line3;//编写程序计算 sentence 中有多少个单词，并指出其中最长和最短的单词。如果有多个最长或最短的单词，则将它们全部输出。//版本一：#include <iostream>#include <string>#include <vector>#include <sstream>using namespace std;int main(){   string line1="we are her pride of 10 she named us:";   string line2="benjamin, phoenix, the  prodigal";   string line3="and perspicacious pacific suzanen";   string sentence=line1+" "+line2+" "+line3;   vector<string> longest_word,smallest_word;   unsigned int count=0;   string::size_type s_size_big=0,s_size_small=0;   string word;   istringstream in_stream(sentence);   cout<<"The sentence is :"<<endl;   while(in_stream>>word)   {      count++;      cout<<word<<" ";      string::size_type size_tmp=word.size();      if(count==1)      {        s_size_big=s_size_small=size_tmp;        longest_word.push_back(word);        smallest_word.push_back(word);      }      else      {         if(size_tmp>s_size_big)         {             s_size_big=size_tmp;             longest_word.clear();             longest_word.push_back(word);         }         else         {            if(size_tmp==s_size_big)            {                longest_word.push_back(word);            }            else            {               if(size_tmp<s_size_small)               {                  s_size_small=size_tmp;                  smallest_word.clear();                  smallest_word.push_back(word);               }               else               {                    if(size_tmp==s_size_small)                    smallest_word.push_back(word);               }            }          }        }     }    cout<<endl;    cout<<"The total number of the words : "<<count<<endl;    cout<<"The longest word is:"<<endl;    for(vector<string>::iterator big_iter=longest_word.begin();big_iter!=longest_word.end();        big_iter++)    cout<<*big_iter<<" ";    cout<<endl;    cout<<"The smallest word is:"<<endl;    for(vector<string>::iterator small_iter=smallest_word.begin();small_iter!=smallest_word.end();        small_iter++)    cout<<*small_iter<<" ";    cout<<endl; }//下面是运用find_first_of和find_first_not_of的版本：/*在答案书的答案上，那个答案是错的！*/#include <iostream>#include <string>#include <vector>using namespace std;int main(){   string line1="we are her pride of 10 she named us:";   string line2="benjamin, phoenix, the  prodigal";   string line3="and perspicacious pacific suzanen";   string spaces(" \t:,\n\v\r\f");//后面都一些转义字符   string sentence=line1+" "+line2+" "+line3;   vector<string> longest_word,smallest_word;   unsigned int count=0;   string word;   string::size_type s_size_big=0,s_size_small=0;   string::size_type start_pos=0, end_pos=0;   while((start_pos=sentence.find_first_not_of(spaces,end_pos))!=string::npos)   {       ++count;       string::size_type size_tmp;       end_pos=sentence.find_first_of(spaces,start_pos); //这个是代码的核心部分       if(end_pos==string::npos)//如果没有匹配的话就返回npos,这是一个非常大的数，比任何的合法的下标都大       size_tmp=sentence.size()-start_pos;       else       size_tmp=end_pos-start_pos;       word.assign(sentence,start_pos,size_tmp);       cout<<"the size of sentence: "<<sentence.size()<<endl;       cout<<word<<" "<<"length:"<<size_tmp<<endl;       if(count==1)      {        s_size_big=s_size_small=size_tmp;        longest_word.push_back(word);        smallest_word.push_back(word);      }      else      {         if(size_tmp>s_size_big)