Algorithm for String Palindrome in C
What is String in C?
In C, a string is a sequence of characters that is terminated by a null character ('\0'). Strings are represented by arrays of characters, where each character is stored in a consecutive memory location.
For example, the following code defines a string variable and initializes it with the characters "Hello, World!" followed by a null character:
charstr[] = "Hello, World!";
Here, the string variable str is an array of characters with a length of 13 (one for each character in the string, plus one for the null character). Note that the size of the array is not explicitly specified, as it is automatically determined by the compiler based on the length of the string literal.
Strings in C can be manipulated using various standard library functions such as strcpy, strcat, strlen, strcmp, and so on. These functions allow you to perform operations such as copying, concatenating, finding the length of, and comparing strings.
What is String Palindrome?
A string is said to be a palindrome if it reads the same backwards as forwards. For example, "racecar" is a palindrome, while "hello" is not.
To check if a string is a palindrome in C, you can compare the characters at opposite ends of the string. Here's an example program that demonstrates this:
//string palindrome program in C
#include <stdio.h>
#include <string.h>
int main() {
char string[100];
inti, j, len, is_palindrome = 1;
printf("Enter a string: ");
fgets(string, 100, stdin);
len = strlen(string) - 1; // subtract 1 to exclude the newline character
for (i = 0, j = len - 1; i<len/2; i++, j--) {
if (string[i] != string[j]) {
is_palindrome = 0;
break;
}
}
if (is_palindrome) {
printf("%s is a palindrome.\n", string);
}
else {
printf("%s is not a palindrome.\n", string);
}
return 0;
}
Output:
Enter a string: 12342
12342 is not a palindrome
Explanation:
In this program, we first declare a character array to store the input string, and use fgets to read the input from the user. We then calculate the length of the string using strlen.
Next, we use a loop that iterates over the first half of the string, comparing characters from both ends to check if the string is a palindrome. If a mismatch is found, we set the is_palindrome flag to 0 and break out of the loop.
Finally, we print the appropriate message based on the value of the is_palindrome flag.
Algorithm of String Palindrome
Here is an algorithm of how to check if a string is a palindrome in C:
- Declare a character array to store the input string.
- Read the input string from the user using a suitable input function like fgets or scanf.
- Determine the length of the string using the strlen function.
- Initialize two variables i and j to the first and last indices of the string respectively.
- Iterate over the string using a loop that runs from i=0 to i<len/2.
- Inside the loop, check if string[i] is equal to string[j]. If not, the string is not a palindrome.
- If the loop completes without finding a mismatch, the string is a palindrome.
- Print the appropriate message based on the result.
Why do we use String Palindrome in C?
We use the concept of string palindrome in C (and in programming in general) to solve a variety of problems.
One common use case is in data validation, where we need to check if a user input is a palindrome or not. For example, we may need to validate a password that requires the user to enter a palindrome string as part of the password.
Another use case is in text processing and manipulation. For example, we may need to find all the palindrome substrings in a given string, or to reorder the characters in a string to form a palindrome.
In addition, the concept of string palindrome is often used as a programming exercise to help beginners improve their programming skills. Checking whether a string is a palindrome requires basic string manipulation and control flow statements, making it a good problem for practicing fundamental programming concepts.