24(March) Insert an Element at the Bottom of a Stack

24. Insert an Element at the Bottom of a Stack

The problem can be found at the following link: Question Link

Problem Description

You are given a stack st of (n) integers and an element (x). You have to insert (x) at the bottom of the given stack.

Example:

Input:

n = 5
x = 2
st = {4,3,2,1,8}

Output:

{2,4,3,2,1,8}

Explanation: After insertion of 2, the final stack will be {2,4,3,2,1,8}.

My Approach

1. Insertion Process:

   • Create a temporary stack tmp.

   • Push all elements from the original stack st to the temporary stack tmp.

   • Push the new element (x) to the bottom of the stack st.

   • Push back all elements from the temporary stack tmp to the original stack st.

Time and Auxiliary Space Complexity

• Expected Time Complexity: O(n), where (n) is the number of elements in the stack.

• Expected Auxiliary Space Complexity: O(n), as we use a temporary stack to store the elements.

Code (C++)

class Solution {
public:
    stack<int> insertAtBottom(stack<int> st, int x) {
        stack<int> tmp;

        // Push all elements from the original stack to a temporary stack
        while (!st.empty()) {
            tmp.push(st.top());
            st.pop();
        }

        // Push the new element to the bottom of the stack
        st.push(x);

        // Push back all elements from the temporary stack to the original stack
        while (!tmp.empty()) {
            st.push(tmp.top());
            tmp.pop();
        }

        return st;
    }
};

Contribution and Support

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