#include <iostream>
#include <string.h>
using namespace std;
char arr[20] = {0};
int top = -1;
void push(char a)
{
arr[++top] = a;
}
char pop()
{
if(top == -1) return '\0';
return arr[top--];
}
void insertatbottom(char op)
{
char op2 = pop();
if(op2 =='\0') { push(op); return ;}
insertatbottom(op);
push(op2);
}
void reverse()
{
char op = pop();
if(op =='\0') return;
reverse();
insertatbottom(op);
}
int main() {
// your code goes here
push('a');
push('b');
push('c');
cout<<arr[2]<<arr[1]<<arr[0];
reverse();
cout<<arr[2]<<arr[1]<<arr[0];
return 0;
}
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