详解C++编程中向函数传递引用参数的用法

// references_to_pointers.cpp
// compile with: /EHsc

#include <iostream>
#include <string>

// STL namespace
using namespace std;

enum {
  sizeOfBuffer = 132
};

// Define a binary tree structure.
struct BTree {
  char *szText;
  BTree *Left;
  BTree *Right;
};

// Define a pointer to the root of the tree.
BTree *btRoot = 0;

int Add1( BTree **Root, char *szToAdd );
int Add2( BTree*& Root, char *szToAdd );
void PrintTree( BTree* btRoot );

int main( int argc, char *argv[] ) {
  // Usage message
  if( argc < 2 ) {
   cerr << "Usage: Refptr [1 | 2]" << "n";
   cerr << "nwhere:n";
   cerr << "1 uses double indirectionn";
   cerr << "2 uses a reference to a pointer.n";
   cerr << "nInput is from stdin.n";
   return 1;
  }

  char *szBuf = new char[sizeOfBuffer];
  if (szBuf == NULL) {
   cerr << "Out of memory!n";
   return -1;
  }

  // Read a text file from the standard input device and
  // build a binary tree.
  //while( !cin.eof() ) 
  {
   cin.get( szBuf, sizeOfBuffer, 'n' );
   cin.get();

   if ( strlen( szBuf ) ) {
     switch ( *argv[1] ) {
      // Method 1: Use double indirection.
      case '1':
        Add1( &btRoot, szBuf );
        break;
      // Method 2: Use reference to a pointer.
      case '2':
        Add2( btRoot, szBuf );
        break;
      default:
        cerr << "Illegal value '"
         << *argv[1]
         << "' supplied for add method.n"
           << "Choose 1 or 2.n";
        return -1;
     }
   }
  }
  // Display the sorted list.
  PrintTree( btRoot );
}

// PrintTree: Display the binary tree in order.
void PrintTree( BTree* MybtRoot ) {
  // Traverse the left branch of the tree recursively.
  if ( btRoot->Left )
   PrintTree( btRoot->Left );

  // Print the current node.
  cout << btRoot->szText << "n";

  // Traverse the right branch of the tree recursively.
  if ( btRoot->Right )
   PrintTree( btRoot->Right );
}

// Add1: Add a node to the binary tree.
//    Uses double indirection.
int Add1( BTree **Root, char *szToAdd ) {
  if ( (*Root) == 0 ) {
   (*Root) = new BTree;
   (*Root)->Left = 0;
   (*Root)->Right = 0;
   (*Root)->szText = new char[strlen( szToAdd ) + 1];
   strcpy_s((*Root)->szText, (strlen( szToAdd ) + 1), szToAdd );
   return 1;
  }
  else {
   if ( strcmp( (*Root)->szText, szToAdd ) > 0 )
     return Add1( &((*Root)->Left), szToAdd );
   else
     return Add1( &((*Root)->Right), szToAdd );
  }
}

// Add2: Add a node to the binary tree.
//    Uses reference to pointer
int Add2( BTree*& Root, char *szToAdd ) {
  if ( Root == 0 ) {
   Root = new BTree;
   Root->Left = 0;
   Root->Right = 0;
   Root->szText = new char[strlen( szToAdd ) + 1];
   strcpy_s( Root->szText, (strlen( szToAdd ) + 1), szToAdd );
   return 1;
  }
  else {
   if ( strcmp( Root->szText, szToAdd ) > 0 )
     return Add2( Root->Left, szToAdd );
   else
     return Add2( Root->Right, szToAdd );
  }
}

								 
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