Recursively reverse a stack - c++

Question

I need to reverse a stack using recursion in C++. I can only use pop, push, and reverseStack, no additional functions such as insertAtBottom which I've found while search stackoverflow and the web.
I've tried:
void Stack::reverseStack(){
if (isEmpty())
return;
else{
int x;
pop(x);
reverseStack();
push(x);
}
}
but this creates a stack exactly the same as the original.

Answer 1

You will need to implement a function to insert an item at the bottom an example is
void Stack::insertAtBottom(int item) {
if(isEmpty())
push(item);
else {
int x;
pop(x);
insertAtBottom(item);
push(x);
}
}
At which point you can implement your reverse as follows
void Stack::reverseStack(){
if (isEmpty())
return;
else{
int x;
pop(x);
reverseStack();
insertAtBottom(x);
}
}
EDIT:
If they need to be in one function, the following is a combination of the two
void Stack::reverseStack(bool reverse=true,int item=0){
if(reverse) {
if (isEmpty())
return;
else{
int x;
pop(x);
reverseStack();
reverseStack(false,x);
}
} else {
if(isEmpty())
push(item);
else {
int x;
pop(x);
reverseStack(false,item);
push(x);
}
}
}
Cheers!

Answer 2

#include <iostream>
#include <stack>
using namespace std;
stack<int> S, R; // S is original stack, R is reversed stack
void reverseStack() {
if(!S.empty()) {
R.push(S.top());
S.pop();
reverseStack();
}
return;
}
int main() {
S.push(1);
S.push(2);
S.push(3);
S.push(4);
S.push(5);
reverseStack();
// Check if R is reversed
while(!R.empty()) {
cout << R.top() << " ";
R.pop();
}
return 0;
}
Hope this helps!

Answer 3

here is a solution to this problem in C language:
#include <stdio.h>
// functions that can be used push(), pop(), and isEmpty()
// the idea is to hold all the values in Function Call Stack until the stack becomes empty.
//When the stack becomes empty, we insert all the held items one by one at the bottom of the stack
// stack-> 1 2 3 4 becomes 4 3 2 1 when we print
#define size 4
int stk[size];
int top = -1;
void insertAtLast(int element);
int isStackFull()
{
if(top == size - 1)
return 1;
return 0;
}
void push(int val)
{
if(isStackFull()==1)
return;
else
//Task 2: Complete the logic
stk[++top] = val;
}
int isStackEmpty()
{
//Task 1: Write logic for isStackEmpty()
if (top==-1)
return 1;
return 0;
}
int pop()
{
if(isStackEmpty()==1)
return -1;
else
//Task 2: Complete the logic
return stk[top--];
}
void reverse(){
if(isStackEmpty()==1){
return;
}
int temp=pop();
reverse();
insertAtLast(temp);
}
void insertAtLast(int element){
if(isStackEmpty()==1){
push(element); //imp
return;
}
int topElements=pop(); //imp
insertAtLast(element); //imp
push(topElements);
}
int main() {
push(4);
push(3);
push(2);
push(1);
for(int i=0;i<size;i++){
printf("%d ", stk[i]);
}
printf("\n");
reverse();
for(int i=0;i<size;i++){
printf("%d ", stk[i]);
}
return 0;
}