cpp primer 验证 p346页

#include <string>
#include <vector>
#include <iostream>
#include <algorithm>
using namespace std;
string make_plural(size_t ctr,const string &word, const string &ending)
{
	return (ctr<=1) ? word : word+ending;	//make_plural(wc, "word ", "s ")当输入中文本中
																//word数大于一是在word后加s，为words为word的复数！
}
//comparison function to be used to sort by word length
bool is_shorter(const string &s1,const string &s2)
{
	return s1.size()<s2.size();
}
//determine whether a length of a given word is 6 or more
bool  GT6(const string &s)
{
	return s.size()>=6;
}
//main
int main()
{
	vector<string> words;
	//copy contents of each book into a single vector
	string next_word;
	while (cin>>next_word)
	{
		//insert next book's content at end of words
		words.push_back(next_word);
	}
	//sort words alphabetically for finding the duplicates
	sort(words.begin(),words.end());
	//eliminate duplicate words
	vector<string>::iterator end_unique=unique(words.begin(),words.end());
	words.erase(end_unique,words.end());
	stable_sort(words.begin(),words.end(),is_shorter);
	vector<string>::size_type wc=count_if(words.begin(),words.end(),GT6);
	cout<<wc<<"  "<<make_plural(wc,"word","s")
		<<" 6 characters or longer"<<endl;
}