Recursive array with a push

Question

Can someone show me where I am going wrong within this Code Academy problem. I'm having a world of trouble with Recursion and am only vaguely beginning to understand how it works at a fundamental level... The first set of code is what I have written followed by the same code with the blanks I have tried to fill in.

Fill in the blanks: Write a conditional statement for the base case of multiplyEach(). We want to end the recursion when there are no more values in stack. Then we want to return the variable int, since this represents the last value evaluated. Complete the recursive case with a recursive call to the function, without any arguments.

Blank Problem with fill-in-the-blanks (___):

var stack = [];

function countDown(int) {
  stack.push(int);
  if (int === 1) {  
    return 1;
  }
    return countDown(int - 1);
}

function multiplyEach() {
  // Remove the last value of the stack 
  // and assign it to the variable int
  int = stack.pop();
  x = stack.length;
  // Base case
  if (___) {
    return ___;
  }
  // Recursive case
  else {
    stack[x - 1] = int * stack[x - 1];
    return ___;
  }
}

// Call the function countDown(7)
countDown(7);
// And then print out the value returned by multiplyEach()
console.log(multiplyEach());

This is my Try:

var stack = [];

function countDown(int) {
  stack.push(int);
  if (int === 1) {  
    return 1;
  }
    return countDown(int - 1);
}

function multiplyEach() {
  // Remove the last value of the stack 
  // and assign it to the variable int
  int = stack.pop(int);
  x = stack.length;
  // Base case
  if (x === 0) {
    return int;
  }
  // Recursive case
  else {
    stack[x - 1] = int * stack[x - 1];
    return multiplyEach(stack);
  }
}

// Call the function countDown(7)
countDown(7);
// And then print out the value returned by multiplyEach()
console.log(multiplyEach());

Thanks!

Are you familiar with the debugger? It allows you to step through your code line by line and see what's happening, inspect variables etc. — Evan Trimboli
– Evan Trimboli, Commented May 29, 2016 at 20:34

Community · Accepted Answer · 2017-05-23 12:22:39Z

4

You filled in the blanks correctly!

There is just one bug you introduced in a part of the code you did not have to touch:

Replace:

int = stack.pop(int);

with:

var int = stack.pop();

Because pop returns the value you need. There is no need to pass anything.

Also, you passed the stack argument to a function that does not take that argument (the variable is global). This does no harm, but to avoid confusion, it is better to call the function without arguments, as it is supposed to be:

   return multiplyEach();

Some side-comments on the code you have been provided with:

it is bad practice to name a variable int as it might become a reserved word in future versions of JavaScript;
That same variable should better be declared locally to the function, as now it is created in the global scope. So with var: var int = ...

edited May 23, 2017 at 12:22

CommunityBot

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answered May 29, 2016 at 21:11

trincot

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3 Comments

Evan Trimboli Over a year ago

Probably also worth noting that int should be a local variable in that function.

Patrick Evans Over a year ago

Also multiplyEach(stack) doesn't need the passed argument either as it uses the global variable stack

trincot Over a year ago

Right you are! Updated.

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