Find last prime number occur before enter number

These tricky kinds of c++ programs can be given in quiz.
    Tell a prime number which exist before an entered  number

    Where the entered number can be a prime number or not

For example:

Input: 11

Output: last prime number is 7

or

Input: 8

Output: Last prime number is 7


C++ CODE



#include<iostream>
using namespace std;
int main()
{
 int num,count=0;
 cout<<"Enter number to find last prime number occurs before it: ";
 cin>>num;
  for( int a=num-1;a>=1;a--)
  {
   for(int b=2;b<a;b++)
      {
       if(a%b==0)
       count++;
       }
       if(count==0)
       {
      if(a==1)
       {
       cout<<"no prime number less than 2";
       break;
     }
      cout<<a<<" is the last prime number before entered number";
       break;
       }
       count=0;
}
return 0;
}

 Sample output:

Image of Code:

 

Program to swap two variables without using third or temp variable

Program Logic Steps:

• Store sum of both in var1.

• Subtract var2 from var1 and store it in var2 (now var2 has value of var1) .

•     Subtract var2 from var1 and store it in var1 (now var1 has    value of var2).
•  

Image View of Code

C++ code to swap two variables without using third variable:

#include<iostream>

using namespace std;

int main()

{

int var1, var2;

 cout<<"Enter value for first integer:  ";

 cin>>var1;

 cout<<"Enter value for second integer:  ";

 cin>>var2;

 cout<<" Values Before swapping:  "<<endl;

 cout<<"First Integer ="<<var1<<endl;

 cout<<"Second Interger ="<<var2<<endl;

              var1=var1+var2;

              var2=var1-var2;

              var1=var1-var2;

 cout<<" Values After swapping:  "<<endl;

 cout<<"First Integer ="<<var1<<endl;

 cout<<"Second Interger ="<<var2<<endl;

    return 0;

}



Sample Output

 Image view of code: