So hey, in this article we are going to learn to insert an element at the Bottom of a Stack

Question Link: https://practice.geeksforgeeks.org/problems/insert-an-element-at-the-bottom-of-a-stack/1

Question Explanation

Inserting an element at the bottom of a stack refers to a specific operation where a new element is added to the bottom-most position in a stack, effectively pushing all the existing elements up by one position. This operation is typically implemented using a recursive approach, as demonstrated in the code provided in the previous response.

Code

void solve(stack<int>& s, int x) {
    //base case
    if(s.empty()) {
        s.push(x);
        return ;
    }
    int num = s.top();
    s.pop();
    //recursive call
    solve(s, x);
    s.push(num);
}
stack<int> pushAtBottom(stack<int>& myStack, int x) 
{
    solve(myStack, x);
    return myStack;
}

Code Explanation

The given code implements a function pushAtBottom that inserts an element x at the bottom of a stack myStack using a recursive approach.

The function solve is a recursive helper function that pops elements from the stack s until it becomes empty, and then pushes the element x to the stack. The recursion is used to temporarily remove all the elements from the stack, and then push them back after the desired element x has been inserted at the bottom.

Here's how the code works:

1. The base case of the recursion is when the stack s is empty. In that case, the element x is directly pushed to the stack using s.push(x), and the function returns.

2. Otherwise, an element num is popped from the top of the stack using s.top() and s.pop(). This element is temporarily stored to be pushed back later.

3. The function solve is recursively called with the same stack s and the element x.

4. After the recursion completes, the element num is pushed back to the stack using s.push(num). This ensures that element x is inserted at the bottom of the stack, as all the elements above it have been temporarily removed and pushed back.

5. Finally, the pushAtBottom function calls solve with the given stack myStack and the element x, and returns the modified stack myStack with the element x inserted at the bottom.

This code can be useful in scenarios where you need to insert an element at the bottom of a stack, which can be used in various stack manipulation operations or algorithms. It's important to note that using recursion for stack manipulation should be done with caution to avoid stack overflow errors, and proper handling of edge cases and error conditions should be considered in practical implementations.