Palindrome String without Built-in Function in C

This is a C program to check a given string is palindrome without using the Built-in Function.

Problem Description

This program accepts a string and checks whether a given string is palindrome without using the built-in function.

Problem Solution

1. Take a string as input and store it in the array.
2. Reverse the string and store it in another array.
3. Compare both the arrays.

Program/Source Code

Here is source code of the C program to check a given string is palindrome without using the Built-in Function .The C program is successfully compiled and run on a Linux system. The program output is also shown below.

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/*
```

 * C program to find the length of a string without using the

 * built-in function also check whether it is a palindrome

```
 */
```
```
#include <stdio.h>
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#include <string.h>
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```
 
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```
void main()
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{
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    char string[25], reverse_string[25] = {'\0'};

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    int i, length = 0, flag = 0;
```
```
 
```
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    printf("Enter a string \n");
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    gets(string);
```

    /*  keep going through each character of the string till its end */

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    for (i = 0; string[i] != '\0'; i++)
```
```
    {
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        length++;
```
```
    }
```

    printf("The length of the string '%s' = %d\n", string, length);

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    for (i = length - 1; i >= 0 ; i--)
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    {
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        reverse_string[length - i - 1] = string[i];

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    }
```

   /*  Check if the string is a Palindrome */

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    for (flag = 1, i = 0; i < length ; i++)

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    {
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        if (reverse_string[i] != string[i])

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            flag = 0;
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    }
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    if (flag == 1)
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       printf ("%s is a palindrome \n", string);

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

```
}
```

Program Explanation

1. Take a string as input and store it in the array string[].
2. Store the same string into the another array reverse_string[] in the reverse fashion.
3. Using for loop compare the elements of both the arrays.
4. If all the elements of the array are same, then it is a palindrome. Otherwise it is not a palindrome.

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Runtime Test Cases

 
Enter a string
how  are you
The length of the string 'how  are you' = 12
how  are you is not a palindrome
 
 
Enter a string
madam
The length of the string 'madam' = 5
madam is a palindrome
 
 
Enter a string
mam
The length of the string 'mam' = 3
mam is a palindrome

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If you wish to look at other example programs on Strings, go to C Programming Examples on Strings. If you wish to look at programming examples on all topics, go to C Programming Examples.

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