C Program to Check String is Palindrome using Stack

This is a C Program to identify whether the string is palindrome or not using stack.

Problem Description

This program takes a string and checks whether the string is palindrome or not using stack.

Problem Solution

1. Take a string as input.
2. Store the string in the stack array.
3. Check whether the string is palindrome or not.

Program/Source Code

Here is source code of the C Program to identify whether the string is palindrome or not using stack. The C program is successfully compiled and run on a Linux system. The program output is also shown below.

```
/*
```

 * C Program to Identify whether the String is Palindrome or not using Stack

```
 */
```
```
#include <stdio.h>
```
```
#include <stdlib.h>
```
```
#include <string.h>
```
```
#define MAX 50
```
```
 
```
```
int top = -1, front = 0;
```
```
int stack[MAX];
```
```
void push(char);
```
```
void pop();
```
```
 
```
```
void main()
```
```
{
```
```
    int i, choice;
```
```
    char s[MAX], b;
```
```
    while (1)
```
```
    {
```

        printf("1-enter string\n2-exit\n");

```
        printf("enter your choice\n");
```
```
        scanf("%d", &choice);
```
```
        switch (choice)
```
```
        {
```
```
        case 1:
```

            printf("Enter the String\n");

```
            scanf("%s", s);
```

            for (i = 0;s[i] != '\0';i++)

```
            {
```
```
                b = s[i];
```
```
                push(b);
```
```
            }
```

            for (i = 0;i < (strlen(s) / 2);i++)

```
            {
```

                if (stack[top] == stack[front])

```
                {
```
```
                    pop();
```
```
                    front++;
```
```
                }
```
```
                else
```
```
                {
```

                    printf("%s is not a palindrome\n", s);

```
                    break; 
```
```
                }
```
```
            }
```

            if ((strlen(s) / 2)  =  =  front)

                printf("%s is palindrome\n",  s);

```
            front  =  0;
```
```
            top  =  -1;
```
```
            break;
```
```
        case 2:
```
```
            exit(0);
```
```
        default:
```

            printf("enter correct choice\n");

```
        }
```
```
    }
```
```
}
```
```
 
```
```
/* to push a character into stack */
```
```
void push(char a)
```
```
{
```
```
    top++;
```
```
    stack[top]  =  a;
```
```
}
```
```
 
```
```
/* to delete an element in stack */
```
```
void pop()
```
```
{
```
```
    top--;
```
```
}
```

Program Explanation

1. Take a string as input and store it in the array s[].
2. Load each character of the array s[] into the array stack[].
3. Use variables front and top to represent the last and top element of the array stack[].
4. Using for loop compare the top and last element of the array stack[]. If they are equal, then delete the top element, increment the variable front by 1 and compare again.
5. If they are not equal, then print the output as “It is not a palindrome”.
6. Compare the elements in the steps 4-5 upto the middle element of the array stack[].
7. If every characters of the array is equal, then it is a paliandrome.

Runtime Test Cases

1-enter string
2-exit
enter your choice
1
Enter the String
madam
madam is palindrome
1-enter string
2-exit
enter your choice
1
Enter the String
ugesh
ugesh is not a palindrome
1-enter string
2-exit
enter your choice
1
Enter the String
abccba
abccba is palindrome
1-enter string
2-exit
enter your choice
1
Enter the String
abdbca
abdbca is not a palindrome
1-enter string
2-exit
enter your choice
2

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