Palindrome Program in C language
Introduction:
Write a C program to check or detect given string is Palindrome or not ( Palindrome Program in C ).
A palindrome is a word or other sequence of characters which reads the same backward as forward.
Examples of String Palindromes :
madam, wow, racecar, stats, etc.
Examples:
The program should accept a String as input and check if it is a Palindrome or not.
Here are few example expected input and outputs of program.
Example 1:
Input:
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Enter String to test : racecar |
Output:
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Given string racecar is a Palindrome |
The string racecar is palindrome, As we can create the same string in forward direction and backward direction.
Example 2:
Input:
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Enter String to test : picture |
Output:
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Given string picture is not a Palindrome |
Example 3:
Input:
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Enter String to test : tenet |
Output:
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Given string tenet is a Palindrome |
Algorithm to Check Palindrome Program :
- We are going to use two pointer/index method.
- One index will start from the beginning and goes in the forward direction and another index will starts from the end and comes in backwards direction.
- Forward index 'i' starts with index and Backward index 'j' starts from 'len-1' ( Here 'len'is the length of the string, So we are starting from the end of the string)
- At each iteration, We are going to check if the character at index 'i' and the character at index 'j' are same or not?
- If the string is palindrome then all characters at index 'i' and index 'j' need to be same ( Until ‘i'<‘j’ condition break), If any of the values at index 'i' and index 'j' are not equal then the string is not a Palindrome.
- If all the characters of 'i' and 'j' are equal until we reach the loop termination i.e ‘i'<‘j’, Then given number is a Palindrome.
Check Palindrome Program in C Language:
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#include<stdio.h> #include<string.h> int main() {     // Declare the desired variables     char str[20];     int i,j,len, cnt;     cnt = 0;      // Take the input string from the user and store it in 'str' variable.     printf("Enter String to test : ");     scanf("%s", str);      // Check the length of the string     len = strlen(str);      // Here is the main logic of the program.     // We are going to use two pointer/index method.     // One will start from the begining and goes forward and another will starts from the end and comes backwards.     // One index 'i' starts with 0 and another index 'j' starts from 'len-1'     // At each iteration, We are going to check if the index 'i' value and index 'j' value are same     // If the string is palindrome it need to be same, If any of the values at index 'i' and index 'j' are not equal then the string is not a Palindrome     // If all the values are equal until we reach the loop termination i.e 'i'<'j', Then given number is a Palindrome.      for(i=0,j=len-1; i<j; i++,j--)     {         // Check if the value at index'i' and 'j' are same         // If same then continue         // If not same means the number is not a Palindrome, Increase the cnt and break out the loop         if(str[i] != str[j])         {             cnt++;             break;         }     }      // Check if the 'cnt' is 0,     // If the 'cnt' is 0, Means all the values at 'i' and 'j' are same.     // which means the given number is Palindrome.     if(cnt == 0)         printf("Given string %s is a Palindrome\n", str);     else         printf("Given string %s is not a Palindrome\n", str);      return 0; } |
Palindrome Program Output:
We are using the GCC compiler on the Ubuntu Linux system. You can use your favourite IDE or Editor.
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// Compile the program using the 'gcc' compiler venkey@venkey $ gcc palindrome.c  // Run the executable file './a.out' venkey@venkey $ ./a.out Enter String to test : wow Given string wow is a Palindrome  // Example 2 venkey@venkey $ ./a.out Enter String to test : racecar Given string racecar is a Palindrome  // Example 3 venkey@venkey $ ./a.out Enter String to test : f1race Given string f1race is not a Palindrome  // Example 4 venkey@venkey $ ./a.out Enter String to test : tenet Given string tenet is a Palindrome  // Example 5 venkey@venkey $ ./a.out Enter String to test : picture Given string picture is not a Palindrome  // Example 6 venkey@venkey $ ./a.out Enter String to test : noon Given string noon is a Palindrome venkey@venkey $ |
Conclusion:
We have discussed about the logic to detect or check the string palindromes using the C programming Language.
