Thread: palindrome - Help needed.

i was able to convert the string into case insensitive and remove special characters but now all i end up with is the same output - it is a palindrome.
please rectify the code and let me know how to fix it.

Code:

#include<iostream>      
//We are creating a string and 2 stacks. Then we push each char of the string into the stack and pop it into an another and compare them.
using namespace std;
struct Stack {
  char *arr;
  int size;
  int capacity;
  int top;

  Stack(int n) {
    capacity = n;
    top = 0;
    size = 0;
    arr = new char;
  } 
  char pop() {
    if (size == 0) {
      cout << "Stack empty" << endl;
      return '0';
    }
    char ch = arr[0];
    for (int i = 0; i < size - 1; i++) {
      arr[i] = arr[i + 1];
    }
    size--;
    return ch;
  }
  void display() {
    if (size == 0) {
      cout << "Stack empty" << endl;
      return;
    }
    cout << "[";
    for (int i = 0; i < size - 1; i++) {
      cout << arr << ",";
    }
    cout << arr[size - 1] << "]" << endl;
  }
  void push(int data) {
    if (size == capacity) {
      cout << "Stack full" << endl;
      return;
    }
    for (int i = size; i > 0; i--) {
      arr[i] = arr[i - 1];
    }
    arr[0] = data;
    size++;
    return;
  }
};

int main()
{
  cout << "Enter letters/words/numbers/phrases :" << endl;
  std::string x;
  std::string temp;
  do {
    getline(cin, x);            //input string
  }
  while (x.empty());            // removing spaces
  x.erase((remove(x.begin(), x.end(), ' ')), x.end());
  std::transform(x.begin(), x.end(), x.begin(),::tolower);  // transform tolower
  for (int i = 0; i < x.size(); ++i) {
    if ((x >= 'a' && x <= 'z') || (x >= 'A' && x <= 'Z')) //initializing condition  
    {
      temp = temp + x;          //passing characters that match condition to temp string from initialized string
    }
  }
  cout << temp;
  int n = x.size();
  Stack stack(n / 2);
  int i = 0;
  for (i = 0; i < n / 2; i++) {
    stack.push(x);
  }
  if (n % 2 != 0) {
    i++;
  }
  while (i < x.size()) {
    if (stack.pop() != x) {
      cout << "The word/phrase/number is not a palindrome" << endl;
      break;
    }
    i++;
  }
  if (i == x.size()) {
    cout << "The word/phrase/number is a palindrome" << endl;
  }
}

Can you post your code again, but this time using "copy as text" and/or "paste as text".
I tried to fix your post, but it broke your code.

Code:

#include <iostream> 
using namespace std;
struct Stack{
    char *arr;
    int size;
    int capacity;
    int top;
    Stack ( int n ) {
        capacity = n;
        top = 0;
        size = 0;
        arr = new char;
    }
    char pop () {
        if( size == 0) {
            cout << "Stack empty"<< endl;
            return '0';
        }
        char ch = arr[0];
        for(int i = 0; i < size-1; i++ ){
            arr[i] = arr[i+1];
        }
        size--;
        return ch;
    }
    void display(){
        if(size == 0){
            cout<< "Stack empty" << endl;
            return;
        }
        cout <<"[";
        for ( int i = 0; i < size-1; i++ ) {
            cout << arr[i] <<",";
        }
        cout << arr[size-1] <<"]" << endl;
    }
     void push (int data) {
        if( size == capacity ) {
            cout<<"Stack full"<<endl;
            return;
        }
        for( int i = size; i > 0; i--) {
            arr[i] = arr[i-1];
        }
        arr[0] = data;
        size++;
        return;
    }
};
int main(){
    cout << "Enter letters/words/numbers/phrases :" <<endl;
    std :: string x;
    std :: string temp;
    do {
    getline(cin, x); //input string
    }
    while (x.empty () ) ; // removing spaces
    x.erase( (remove(x.begin(),x.end(),' ') ),x.end() );
    std::transform(x.begin(), x.end(), x.begin(), ::tolower); // transform tolower
    for (int i = 0; i < x.size(); ++i)
    {
        if ((x[i] >= 'a' && x[i] <= 'z') || (x[i] >= 'A' && x[i] <= 'Z')) //initializing condition 
        {
            temp = temp + x[i];//passing characters that match condition to temp string from initialized string
        }
    }
    cout << temp;
    int n = x.size();
    Stack stack(n/2);
    int i = 0;
   for(i=0; i < n/2; i++){
        stack.push ( x[i] );
    }
    if(n%2 != 0) {
        i++;
    }
    while (i < x.size() ) {
        if (stack.pop() != x[i]) {
            cout<< "The word/phrase/number is not a palindrome" << endl;
            break;
        }
        i++;
    }
    if ( i == x.size() ) {
        cout<< "The word/phrase/number is a palindrome" << endl;
    }
}

I suppose that was an improvement, at least it was easy to cleanup.

> arr = new char;
You don't allocate the size you requested.

Your assignment clearly states that you need to use TWO stacks, but you only have one.

When you do the test for a palindrome you need to do it with temp, not the original x that still has the extra characters in it. Also, you need to allocate n chars in Stack, not just 1.

Also, your algorithm for the stack is inefficient. There's no need to move the contents of the array back and forth. Instead of adding new elements to the beginning (element 0), add them to the end instead!

> if (S[i] < 'A' || S[i] > 'Z' &&
You've swapped over the && and || compared to post #4 (and broken what you had)

All you needed was another
|| ( x[i] >= '0' && x[i] <= '9' )

Or maybe
Null-terminated byte strings - cppreference.com
if ( isupper(x[i]) || islower(x[i]) || isdigit(x[i]) )