CODEWITHSUNDEEP
cstring
fiftyplus
fiftyplus

Reputation: 561

end of line character is not detected

A simple program, a static string which is used to read the input, then pass it to the function. Just wondering why it can not find the '\0' character using the while(*string!='\0') expression.

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

int is_palindrome(char *string)
{
    int length, mid, end, i;
    length=0;
    if (string == NULL)
        return 0;

    while (string[length] != '\0')
    {
        printf("%c\n", string[length]);
        length++;

    }
    //Not working version
    /*
    while(*string!='\0')
        length++;
    */

    end = length - 1;
    mid = length / 2;
    printf(" end=%d, mid=%d\n", end, mid);
    for (i = 0; i < mid; i++) {
        if (string[i] != string[end]) {
            printf("It's not palindrome\n");
            return 0;
        }
        end--;
    }

    if (i == mid) {
        printf("It's palindrome\n");
        return 1;
    }

    return 0;
}

int main(void)
{
    char string[100];
    printf("Enter a string to test for the parlindrome\n");
    gets(string);

    int length = strlen(string);
    printf("You entered %s,length is %d\n", string, length);
    if (is_palindrome(string))
        ;
    printf("Enter to Quit\n");
    char x;
    scanf("%c", &x);
    return 0;
}

Upvotes: 0

Views: 173

Answers (2)

luser droog
luser droog

Reputation: 19494

Initialize length to 0 before using its value in the while loop.

Or you could use the standard library function strlen().

Also, in the palindrome check, you should probably decrease end at the same you increase i. As it is, you're comparing the characters in the first half each with the same char at the end. This will match strings like "aaaabfa" but not "abcdcba".

Upvotes: 1

AndersK
AndersK

Reputation: 36082

Instead of

while(*string!='\0')
  length++;

write

char* p = string;
while( *p++ )
  length++;

otherwise the pointer will not move and you become stuck in an infinite loop (if the string is not empty). Use p to avoid changing the original pointer.

Also initialize all variables before using them, good rule of thumb.

Upvotes: 3

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