/*
 * Use the recursion and the stack ADT to find strings of the form
 * w$w', where w' = reverse(w).
 */
#include <iostream>
#include "C6-StackA.h"
using namespace std;

int recogStack(string str);
int recogRecursion(string str, int index);

int main()
{
  string str;
  int result;

  cout << "Enter a string of for w$w', where w'=reverse(w): ";
  cin >> str;

  // Check for empty string
  if(str.length() == 0)
    return 0;
  
  // Recognize pattern using recursion
  cout << "Using recursion, the pattern is: ";
  result = recogRecursion(str, 0);
  cout << result << endl;

  //  Recognize pattern using Stack ADT
  cout << "Using stack ADT, the reverse string is: ";
  result = recogStack(str);
  cout << result << endl;
  
  return 0;
}

/*
 * Recursive routine to recognize pattern w$w'
 */
int recogRecursion(string str, int index)
{
  return 0;
}

/*
 * Use stack to  recognize pattern w$w'
 */
int recogStack(string str)
{
  Stack stklist;
  char c;
  int i;
  
  // push each character on the LIFO stack
  for(i=0 ; i<str.length() && str[i]!='$' ; i++)
    stklist.push(str[i]);

  // skip over the '$'
  if(str[i] == '$')
    i++;

  // pop the items from the stack in LIFO order and compare them with the
  // remaining characters in the string to detect pattern w$w'
  while(!stklist.isEmpty() && i<str.length()){
    stklist.pop(c);
    if(c != str[i])
      break;
    i++;
  }

  if(!stklist.isEmpty() || i<str.length())
    return 0;
  return 1;
}