programming-examples/c++/Others/Fig02_09.cpp - Test program for binary search.cpp
2019-11-15 12:59:38 +01:00

46 lines
1.3 KiB
C++

Fig02_09.cpp - Test program for binary search
#include <iostream.h>
#include "vector.h"
const int NOT_FOUND = -1;
/* START: Fig02_09.txt*/
/**
* Performs the standard binary search using two comparisons per level.
* Returns index where item is found or -1 if not found
*/
template <class Comparable>
int binarySearch( const vector<Comparable> & a, const Comparable & x )
{
/* 1*/ int low = 0, high = a.size( ) - 1;
/* 2*/ while( low <= high )
{
/* 3*/ int mid = ( low + high ) / 2;
/* 4*/ if( a[ mid ] < x )
/* 5*/ low = mid + 1;
/* 6*/ else if( a[ mid ] > x )
/* 7*/ high = mid - 1;
else
/* 8*/ return mid; // Found
}
/* 9*/ return NOT_FOUND; // NOT_FOUND is defined as -1
}
/* END */
// Test program
int main( )
{
const int SIZE = 8;
vector<int> a( SIZE );
for( int i = 0; i < SIZE; i++ )
a[ i ] = i * 2;
for( int j = 0; j < SIZE * 2; j++ )
cout << "Found " << j << " at " << binarySearch( a, j ) << endl;
return 0;
}