惨痛教训：string > < 比较的仅仅是头一个字母！！！！

 

#include <iostream>
#include <string>
 using namespace std;
 int HowManyWord(string sentence)
{
    int words=1;
    for(string::size_type i=0;i!=sentence.size();++i)
        if(sentence[i]==' ')
            ++words;
    return words;
}
string LongestWord(string sentence)
{
    string back,longest;
    for(string::size_type i=0;i!=sentence.size();++i)
        if(sentence[i]==' ')
        {
            if(back>longest)\\key problem
\\应该改为back.size()>longest.size()先比第一个字母字母相同让后第二个。。。

                longest=back;
            back="";
        }
        else
        back+=sentence[i];
    return longest;
}
string ShortestWord(string sentence)
{
    string back,shortest="aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa";
    for(string::size_type i=0;i!=sentence.size();++i)
        if(sentence[i]==' ')
        {
            if(back<shortest)
                shortest=back;
            back="";
        }
        else
        back+=sentence[i];
    return shortest;
}
int main()
{
    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;
    cout<<"There are " <<HowManyWord(sentence) <<" words." <<endl;
    cout<<"LongestWord:" <<LongestWord(sentence) <<endl;
    cout<<"ShortestWord:" <<ShortestWord(sentence) <<endl;
    return 0;
}