STL Sample for the Vector Class Using the operat

• The Standard C++ Library included with: - Microsoft Visual C++, 32-bit Edition, version 4.2

SUMMARY

The following sample code illustrates how to define operator < to sort a vector of user-defined types.

MORE INFORMATION

Required Headers

   <vector>
   <algorithm>

Prototypes

   template<class _TYPE, class _A> inline
   bool operator<(const vector<_TYPE, _A>& _X,
                  const vector<_TYPE, _A>& _Y);

Description

The sample declares an empty vector of IDs, a user-defined type. It initializes and adds four IDs to the vector in random order. It sorts them using the operator< defined for ID and generates the newly sorted vector. (Note that it sorts in order of Score, not Name.)

Sample Code

//////////////////////////////////////////////////////////////////////
//
// Compile options needed: /GX
//
//    Opless.cpp -- Illustrates the defining the < operator to sort vectors
//
// Functions:
//
//    operator< - Vector comparison operator.
//
//    vector::begin - Returns an iterator to start traversal of the vector.
//
//    vector::end - Returns an iterator for the last element of the vector.
//
//    vector::iterator - Traverses the vector.
//
//    vector::push_back - Appends (inserts) an element to the end of a
//                        vector, allocating memory for it if necessary.
//
//    sort algorithm - Sorts the vector.
//
// Written by Tom Campbell
// of Microsoft Corporation
// Copyright (c) 1996 Microsoft Corporation. All rights reserved.
//////////////////////////////////////////////////////////////////////

// The debugger can't handle symbols more than 255 characters long.
// STL often creates symbols longer than that.
// When symbols are longer than 255 characters, the warning is disabled.

#include <iostream>
#include <vector>
#include <string>
#include <algorithm>

// The ID class is used for team scoring. It holds each player's name
// and score.

    string Name;
    int Score;
    ID() : Name(""), Score(0) {}
    ID(string NewName, int NewScore) : Name(NewName), Score(NewScore) {}

// IDs will be sorted by Score, not by Name.

    return x.Score < y.Score;

// Define a template class for a vector of IDs.

void main()

    // Declare a dynamically allocated vector of IDs.
    NAMEVECTOR theVector;

    // Iterator is used to loop through the vector.
    NAMEVECTOR::iterator theIterator;

    // Create a pseudo-random vector of players and scores.
    theVector.push_back(ID("Karen Palmer", 2));
    theVector.push_back(ID("Ada Campbell", 1));
    theVector.push_back(ID("John Woloschuk", 3));
    theVector.push_back(ID("Grady Leno", 2));

    // Output the contents of the vector.
    cout << endl << "Players and scores:" << endl;
    for (theIterator = theVector.begin(); theIterator != theVector.end();
         theIterator++)
        cout << theIterator->Score  << "\t"
             << theIterator->Name << endl;
    cout << endl;

    // Sort the vector of players by score.
    sort(theVector.begin(), &theVector[theVector.size()]);

    // Output the contents of the vector in its new, sorted order.
    cout << "Players ranked by score:" << endl;
    for (theIterator = theVector.begin(); theIterator != theVector.end();
         theIterator++)
        cout << theIterator->Score  << "\t"
             << theIterator->Name << endl;
    cout << endl << endl;

Program Output

Players and scores:

2       Karen Palmer
1       Ada Campbell
3       John Woloschuk
2       Grady Leno

1       Ada Campbell
2       Karen Palmer
2       Grady Leno
3       John Woloschuk

REFERENCES

Visual C++ Books Online: Visual C++ Books; C/C++; Standard C++ Library Reference