Is there a way to incrementally increase count in a recursion?

Question

Is there a way to incrementally increase the count for the Tower of Hanoi challenge?

At the moment, the count isn't incrementally increasing. Interestingly, it starts at five and hops around. See the output below.

I tried adding a let count = 0 within the function and adding ++count within the IF statement and outside the recursive function to no avail.

Working code block:

const move = (n, source, destination, buffer, count) => {

  // Verify that there are disks.
  if (n > 0) {

    // Move one disk to buffer rod.
    move(n - 1, source, buffer, destination, ++count);

    // Move nth disk from source to destination.
    destination.push(source.pop())

    // Display progress
    console.log(count, A, B, C, "\n--------------------------")

    // Move the disk (n - 1) from the buffer to the destination.
    move(n - 1, buffer, destination, source, ++count);
  }
};

// Disk starting position
const A = [5, 4, 3, 2, 1]
const B = []
const C = []

// Invoke
move(5, A, C, B, 0);

Output:

5 [ 5, 4, 3, 2 ] [] [ 1 ] 
--------------------------
4 [ 5, 4, 3 ] [ 2 ] [ 1 ] 
--------------------------
6 [ 5, 4, 3 ] [ 2, 1 ] [] 
--------------------------
3 [ 5, 4 ] [ 2, 1 ] [ 3 ] 
--------------------------
6 [ 5, 4, 1 ] [ 2 ] [ 3 ] 
--------------------------
5 [ 5, 4, 1 ] [] [ 3, 2 ] 
--------------------------
7 [ 5, 4 ] [] [ 3, 2, 1 ] 
--------------------------
2 [ 5 ] [ 4 ] [ 3, 2, 1 ] 
--------------------------
6 [ 5 ] [ 4, 1 ] [ 3, 2 ] 
--------------------------
5 [ 5, 2 ] [ 4, 1 ] [ 3 ] 
--------------------------
7 [ 5, 2, 1 ] [ 4 ] [ 3 ] 
--------------------------
4 [ 5, 2, 1 ] [ 4, 3 ] [] 
--------------------------
7 [ 5, 2 ] [ 4, 3 ] [ 1 ] 
--------------------------
6 [ 5 ] [ 4, 3, 2 ] [ 1 ] 
--------------------------

Use a preassigned parameter maybe? So replace count with count = 0 in your function signature. https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Functions/Default_parameters — Berk Kurkcuoglu, Jun 01 '20 at 21:50
@Berk I tried count = 0 and the output is the same. Would adding a preassigned parameter change the outcome even if the invocation includes 0? — peyo, Jun 01 '20 at 21:56
I mean, it starts from 0 then you are incrementing it respectively, if you were to assign it to 0 inside the function it would be 0 each time the recursion occurs, this way you are able increment the value, that was my approach. — Berk Kurkcuoglu, Jun 01 '20 at 21:58

score 0 · Answer 1 · answered Jun 01 '20 at 21:55

Return the value of count and assign it back to the variable.

const move = (n, source, destination, buffer, count) => {

  // Verify that there are disks.
  if (n > 0) {

    // Move one disk to buffer rod.
    count = move(n - 1, source, buffer, destination, ++count);

    // Move nth disk from source to destination.
    destination.push(source.pop())

    // Display progress
    console.log(count, JSON.stringify(A), JSON.stringify(B), JSON.stringify(C), "\n--------------------------")

    // Move the disk (n - 1) from the buffer to the destination.
    count = move(n - 1, buffer, destination, source, ++count);
    
  }
  return count;
};

// Invocate
const A = [5, 4, 3, 2, 1]
const B = []
const C = []

move(5, A, C, B, 0);

Is there a way to incrementally increase count in a recursion?

1 Answers1