STL 使用STL实例

//usealgo.cpp -- using several STL elements
#include <iostream>
#include <string>
#include <vector>
#include <set>
#include <map>
#include <iterator>
#include <algorithm>
#include <cctype>
using namespace std;

char toLower(char ch) { return tolower(ch); }  //转字符
string & ToLower(string & st);   //转小写
void display(const string & s);

int main()
{
　　//读入单词
    vector<string> words;
    cout << "Enter words (enter quit to quit):\n";
    string input;
    while (cin >> input && input != "quit")
        words.push_back(input);

    cout << "You entered the following words:\n";
    for_each(words.begin(), words.end(), display);
    cout << endl;
　　　
　　//存入set联合容器　以便排序　去重复
    // place words in set, converting to lowercase
    set<string> wordset;
    transform(words.begin(), words.end(),
        insert_iterator<set<string> > (wordset, wordset.begin()),
        ToLower);
    cout << "\nAlphabetic list of words:\n";
    for_each(wordset.begin(), wordset.end(), display);
    cout << endl;

　　//存入map联合容器　使值和出现次数　关联起来
　　//该容器可以使用'关键字'做下标　来索引其值
    // place word and frequency in map
    map<string, int> wordmap;
    set<string>::iterator si;
    for (si = wordset.begin(); si != wordset.end(); si++)
        wordmap[*si] = count(words.begin(), words.end(), *si);

    // display map contents
    cout << "\nWord frequency:\n";
    for (si = wordset.begin(); si != wordset.end(); si++)
        cout << *si << ": " << wordmap[*si] << endl;

    return 0;
}

string & ToLower(string & st)
{
    transform(st.begin(), st.end(), st.begin(), toLower);
    return st;
}

void display(const string & s)
{
    cout << s << " ";
}