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