Recursion

Definitions:
A recursive function is a function that calls itself. Every recursive function has a base case and a recursive case. Recursive case must get closer to the base case.

Examples:
- factorial function
- searching a maze
- fibonacci function


input: int, example: 123456789

output: reversed number: 987654321

pseudocode:
printrec n:
  if (n > 0) {
    print last digit
    printrec n / 10
  }

c++:
void printrec(int n)
{
  if (n > 0) {
    cout << n%10;
    printrec(n/10);
  }
}


input: number as int (ex: 12345678)
out: number forward
void printfrec(int n)
{
  if (n > 0) {
    printfrec(n/10);
    cout << n%10;
  }
}



input: number as int (ex: 123)
output: print this number on screen vertically!
1
2
3

void printfrecv(int n)
{
  if (n > 0) {
    printfrecv(n/10);
    cout << n%10 << endl;
  }
}


input: number as int (ex: 123)
output: number backwards and forward: (32123)


void printbackandforth(int n)
{
  if (n > 9) {
    cout << n%10;
    printbackandforth(n/10);
    cout << n%10;
  } else cout << n;
}



void bla1()
{
  cout << "hello" << endl;
  cout << "world" << endl;
}

void bla()
{
  cout << "this" << endl;
  bla1();
  cout << "test" << endl;
}

...
bla()
...


try and implement recursively:
- print number backwards
- print number forward vertically
- print number down and up (32123)


example for maze running:

try (position) {
  if (!marked(position)) {
     mark position;
     try (position north);
     try (position south);
     try (position east);
     try (position west);
     unmark position
     }
  }