2.Control Structures

2.Control Structures

The codes:

// 2.Control Structures

/****************************
1
Control Structures
*/

// custom countdown using while

#include <iostream>
using namespace std;

int main ()
{
  int n;
  cout << "Enter the starting number > ";
  cin >> n;

  while (n>0) {
    cout << n << ", ";
    --n;
  }

  cout << "FIRE!
";
  return 0;
}


// number echoer

#include <iostream>
using namespace std;

int main ()
{
  unsigned long n;
  do {
    cout << "Enter number (0 to end): ";
    cin >> n;
    cout << "You entered: " << n << "
";
  } while (n != 0);
  return 0;
}


// countdown using a for loop
#include <iostream>
using namespace std;
int main ()
{
  for (int n=10; n>0; n--) {
    cout << n << ", ";
  }
  cout << "FIRE!
";
  return 0;
}


// more for...

#include <iostream>
using namespace std;

int main ()
{
  int n,i,sum=0;
  for(n=0,i=100;n!=i;n++,i--)
    sum++;
  cout<<sum<<endl;

  return 0;
}



// break loop example

#include <iostream>
using namespace std;

int main ()
{
  int n;
  for (n=10; n>0; n--)
  {
    cout << n << ", ";
    if (n==3)
    {
      cout << "countdown aborted!";
      break;
    }
  }
  return 0;
}



// continue loop example
#include <iostream>
using namespace std;

int main ()
{
  for (int n=10; n>0; n--) {
    if (n==5) continue;
    cout << n << ", ";
  }
  cout << "FIRE!
";
  return 0;
}



// goto loop example

#include <iostream>
using namespace std;

int main ()
{
  int n=10;
  loop:
  cout << n << ", ";
  n--;
  if (n>0) goto loop;
  cout << "FIRE!
";
  return 0;
}



// selective structure:switch
#include <iostream>
using namespace std;

int main ()
{
  int x;
  srand(int(time(0)));
  x=1+rand()%4;
  switch(x)
  {
    case 1:cout<<1;break;
    case 2:cout<<2;break;
    default:
      cout<<">2";
  }
  cout<<endl;
  x=1+rand()%4;
  switch(x)
  {
    case 1:
    case 2:
      cout << "x is 1, or 2";
      break;
    default:
      cout << "x is not 1,2";
  } 

  return 0;
}


/**********************************
2
Functions (I)
*/

// function example
#include <iostream>
using namespace std;

int addition (int a, int b)
{
  int r;
  r=a+b;
  return (r);
}

int main ()
{
  int z;
  z = addition (5,3);
  cout << "The result is " << z;
  return 0;
}


// function example
#include <iostream>
using namespace std;

int subtraction (int a, int b)
{
  int r;
  r=a-b;
  return (r);
}

int main ()
{
  int x=5, y=3, z;
  z = subtraction (7,2);
  cout << "The first result is " << z << '
';
  cout << "The second result is " << subtraction (7,2) << '
';
  cout << "The third result is " << subtraction (x,y) << '
';
  z= 4 + subtraction (x,y);
  cout << "The fourth result is " << z << '
';
  return 0;
}



// void function example
#include <iostream>
using namespace std;

void printmessage ()
{
  cout << "I'm a function!";
}

int main ()
{
  printmessage ();
  return 0;
}


/*****************************************

3
Functions (II)
*/

// passing parameters by reference
#include <iostream>
using namespace std;

void duplicate (int& a, int& b, int& c)
{
  a*=2;
  b*=2;
  c*=2;
}

int main ()
{
  int x=1, y=3, z=7;
  duplicate (x, y, z);
  cout << "x=" << x << ", y=" << y << ", z=" << z;
  return 0;
}



// more than one returning value
#include <iostream>
using namespace std;

void prevnext (int x, int& prev, int& next)
{
  prev = x-1;
  next = x+1;
}

int main ()
{
  int x=100, y, z;
  prevnext (x, y, z);
  cout << "Previous=" << y << ", Next=" << z;
  return 0;
}


// default values in functions

#include <iostream>
using namespace std;

int divide (int a, int b=2)
{
  int r;
  r=a/b;
  return (r);
}

int main ()
{
  cout << divide (12);
  cout << endl;
  cout << divide (20,4);
  return 0;
}



// overloaded function
#include <iostream>
using namespace std;

int operate (int a, int b)
{
  return (a*b);
}

float operate (float a, float b)
{
  return (a/b);
}

int main ()
{
  int x=5,y=2;
  float n=5.0,m=2.0;
  cout << operate (x,y);
  cout << "
";
  cout << operate (n,m);
  cout << "
";
  return 0;
}



// factorial calculator
#include <iostream>
using namespace std;

long factorial (long a)
{
  if (a > 1)
   return (a * factorial (a-1));
  else
   return (1);
}

int main ()
{
  long number;
  cout << "Please type a number: ";
  cin >> number;
  cout << number << "! = " << factorial (number);
  return 0;
}



// declaring functions prototypes
#include <iostream>
using namespace std;

void odd (int a);
void even (int a);

int main ()
{
  int i;
  do {
    cout << "Type a number (0 to exit): ";
    cin >> i;
    odd (i);
  } while (i!=0);
  return 0;
}

void odd (int a)
{
  if ((a%2)!=0) cout << "Number is odd.
";
  else even (a);
}

void even (int a)
{
  if ((a%2)==0) cout << "Number is even.
";
  else odd (a);
}

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