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// Programmieren 1, Praktikum 2, Aufgabe 5
// Sven Eisenhauer
// 06.11.2004
//
// file: prg1p2_5.cpp
//
// purpose: program to reads 2 integers from keyboard and finds all prime number twins
// between them, like 3 and 5 or 17 and 19
//
#include <iostream>
using std::cin;
using std::cout;
using std::endl;
int main()
{
int iNumberA, iNumberB;
int iMin, iMax;
int iIsPrime1=0;
int iIsPrime2=0;
int iPrime1=0;
int iPrime2=0;
int iToTest=0;
cout << "Please enter 1st number: ";
cin >> iNumberA;
cout << "Please enter 2nd number: ";
cin >> iNumberB;
cout << endl;
// first find out, which is the bigger value.
iMax=iNumberA;
iMin=iNumberB;
if (iNumberB > iNumberA)
{
iMax=iNumberB;
iMin=iNumberA;
}
// First loop: Get all numbers between the 2 entered
for (int iOuterCounter=iMax-1;iOuterCounter>iMin;iOuterCounter--)
{
iIsPrime1=0;
for (int iInnerCounter=iOuterCounter-1;iInnerCounter>1;iInnerCounter--)
{
if ( 0 == iOuterCounter%iInnerCounter)
iIsPrime1=1; // actual number is NOT a prime
}// end inner for routine
if (0 == iIsPrime1)
{
iPrime1=iOuterCounter;
// now test, if iPrime1 - 2 is a prime
iIsPrime2 = 0;
iToTest = iOuterCounter - 2;
for (int iInnerCounter2=iToTest-1;iInnerCounter2>1;iInnerCounter2--)
{
if (0 == iToTest%iInnerCounter2)
iIsPrime2=1;
}
if (0 == iIsPrime2)
iPrime2=iToTest;
if ((0 == iIsPrime1) && (0 == iIsPrime2) && (iPrime2 > iMin))
cout << iPrime1 << "\t" << iPrime2 << endl;
}
// if (iIsPrime1 && iIsPrime2)
// cout << iPrime1 << "\t" << iPrime2 << endl;
}
// system ("pause");
return 0;
}// end main
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