C++ Primer 课后习题9.39 统计单词个数并记录最大单词和最短单词

习题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 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。如果有多个最短或者最长单词，则将他们全部输出。

代码：

#include <iostream>
#include <vector>
#include <list>
#include <string>
#include <deque>
#include <algorithm>
#include <sstream>
using namespace std;

int main(int argc, char **argv)
{    
    string num("0123456789");
    string alpha("abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ");
    string alphanum = num + alpha;
    string line1 = "We were her pride of 10 she named us:";
    string line2 = "Benjamin, Phoenix, the Prodigal";
    string line3 = "and perspicacious perspicacious pacific Suzanne";
    string sentence = line1 + ' ' + line2 + ' ' + line3;
    stringstream ss;
    ss.str(sentence);
    string str;
    string strMax;
    string strMin;
    vector<string> vStrMax;
    vector<string> vStrMin;
    int sum = 0;
    while (ss>>str)
    {
        sum++;
        string::size_type pos = 0;
        //删除非字母字符
        while ((pos = str.find_first_not_of(alphanum,pos)) != string::npos)
        {
            str.erase(pos);            
        }
        //比较获取最大单词
        if (str.size() > strMax.size())
        {    
            strMax = str;
            vStrMax.clear();
            vStrMax.push_back(str);
        }else if (str.size() == strMax.size())
        {            
            vStrMax.push_back(str);            
        }
        //比较获取最小单词，注意strMin第一次大小为0
        if (str.size() < strMin.size() || strMin.size() == 0)
        {    
            strMin = str;
            vStrMin.clear();
            vStrMin.push_back(str);
        }else if (str.size() == strMin.size())
        {            
            vStrMin.push_back(str);            
        }        
    }
    return 0;
}

总结：（1）使用字符串流处理字符串，获取单个单词；

　　　（2）使用string的find_first_not_of()方法除去“，：”非单词字符。