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C & C++ Multimedia Cyber Classroom
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C and C++ Multimedia Cyber Classroom (Prentice Hall) (1998).iso
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src
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fig04_20.jar
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Ch04
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Fig04_20
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Fig04_20.cpp
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C/C++ Source or Header
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1997-10-13
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2KB
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85 lines
// Fig. 4.20: fig04_20.cpp
// Binary search of an array
#include <iostream.h>
#include <iomanip.h>
int binarySearch( int [], int, int, int, int );
void printHeader( int );
void printRow( int [], int, int, int, int );
int main()
{
const int arraySize = 15;
int a[ arraySize ], key, result;
for ( int i = 0; i < arraySize; i++ )
a[ i ] = 2 * i; // place some data in array
cout << "Enter a number between 0 and 28: ";
cin >> key;
printHeader( arraySize );
result = binarySearch( a, key, 0, arraySize - 1, arraySize );
if ( result != -1 )
cout << '\n' << key << " found in array element "
<< result << endl;
else
cout << '\n' << key << " not found" << endl;
return 0;
}
// Binary search
int binarySearch( int b[], int searchKey, int low, int high,
int size )
{
int middle;
while ( low <= high ) {
middle = ( low + high ) / 2;
printRow( b, low, middle, high, size );
if ( searchKey == b[ middle ] ) // match
return middle;
else if ( searchKey < b[ middle ] )
high = middle - 1; // search low end of array
else
low = middle + 1; // search high end of array
}
return -1; // searchKey not found
}
// Print a header for the output
void printHeader( int size )
{
cout << "\nSubscripts:\n";
for ( int i = 0; i < size; i++ )
cout << setw( 3 ) << i << ' ';
cout << '\n';
for ( i = 1; i <= 4 * size; i++ )
cout << '-';
cout << endl;
}
// Print one row of output showing the current
// part of the array being processed.
void printRow( int b[], int low, int mid, int high, int size )
{
for ( int i = 0; i < size; i++ )
if ( i < low || i > high )
cout << " ";
else if ( i == mid ) // mark middle value
cout << setw( 3 ) << b[ i ] << '*';
else
cout << setw( 3 ) << b[ i ] << ' ';
cout << endl;
}