A sample for map

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#string #iterator #character #each #insert #output

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本文通过一个具体的示例展示了如何使用C++ STL中的map容器进行插入(insert)、查找(find)及判断结束(end)等基本操作。具体实现包括创建一个整数到字符串的映射，并读取用户输入的一串数字，将每个数字转换为其对应的英文单词。

map::insert, map::find, and map::end (STL Sample) @import url(MS-ITS:dsmsdn.chm::/html/msdn_ie4.css);

//////////////////////////////////////////////////////////////////////
//
// Compile options needed: None
//
// <filename> :  main.cpp
//
// Functions:
//
//      end
//      find
//      insert
//////////////////////////////////////////////////////////////////////

#pragma warning(disable:4786)

#include <iostream>
#include <string>
#include <map>

using namespace std;


typedef map<int, string, less<int> > INT2STRING;

void main()
{
// 1. Create a map of ints to strings
    INT2STRING theMap;
    INT2STRING::iterator theIterator;
    string theString = "";
    int index;

// Fill it with the digits 0 - 9, each mapped to its string counterpart
// Note: value_type is a pair for maps...
    theMap.insert(INT2STRING::value_type(0,"Zero"));
    theMap.insert(INT2STRING::value_type(1,"One"));
    theMap.insert(INT2STRING::value_type(2,"Two"));
    theMap.insert(INT2STRING::value_type(3,"Three"));
    theMap.insert(INT2STRING::value_type(4,"Four"));
    theMap.insert(INT2STRING::value_type(5,"Five"));
    theMap.insert(INT2STRING::value_type(6,"Six"));
    theMap.insert(INT2STRING::value_type(7,"Seven"));
    theMap.insert(INT2STRING::value_type(8,"Eight"));
    theMap.insert(INT2STRING::value_type(9,"Nine"));

// Read a Number from the user and print it back as words
    for( ; ; )
    {
        cout << "Enter /"q/" to quit, or enter a Number: ";
        cin >> theString;
        if(theString == "q")
            break;
        // extract each digit from the string, find its corresponding
        // entry in the map (the word equivalent) and print it
        for(index = 0; index < theString.length(); index++){
            theIterator = theMap.find(theString[index] - '0');
            if(theIterator != theMap.end() )    // is 0 - 9
                cout << (*theIterator).second << " ";
            else    // some character other than 0 - 9
                cout << "[err] ";
        }
        cout << endl;
    }
}

Program Output is:

Enter "q" to quit, or enter a Number: 22

Two Two

Enter "q" to quit, or enter a Number: 33

Three Three

Enter "q" to quit, or enter a Number: 456

Four Five Six

Enter "q" to quit, or enter a Number: q