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Recursion for Coding Interviews in JavaScript

Solution Review: Reverse a Stack

Explore how to reverse a stack using recursion in JavaScript without using additional stacks or data structures. Learn the roles of the reverse and insertAtBottom functions, understand their base cases and recursive calls, and see how elements are moved recursively to achieve the reversed stack.

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Solution: Using Recursion

Javascript (babel-node)
import Stack from './stack.js'
function insertAtBottom(stack, item) { // Creating a helper function
  // Base case
  if (stack.isEmpty() == true) {
    stack.push(item);
  }
  // Recursive case
  else {
    var temp = stack.pop();
    insertAtBottom(stack, item);
    stack.push(temp);
  } 
}
 
function reverse(testVariable) {
  // Recursive case
  if (testVariable.isEmpty() == false) {
    var temp = testVariable.pop();
    reverse(testVariable);
    insertAtBottom(testVariable, temp);
  }
}
myStack = new Stack(); 
myStack.push(2); 
myStack.push(3); 
myStack.push(5); 
myStack.push(8); // <---- 8 will be at the top of the stack because it was pushed last
console.log("Original Stack: ");
console.log(myStack.getStack());
reverse(myStack);
console.log("Reversed Stack: ");
console.log(myStack.getStack());

Explanation

A simple solution to reversing a stack is to create another stack. Pop elements from the old stack into the new stack and we will have the reversed contents in the new stack.

However, the problem statement asked us specifically to not use any other data structure or stack. ...