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)