CODEWITHSUNDEEP
c
Michael
Michael

Reputation: 721

C substring two equal characters not matching

am writing a program to find a substring in a string. For some strange reason, during comparison of one character to another, two similar characters do not match. I'm not sure if this is some sort of bug. Here's the code:

#include <stdio.h>
int first_char_compare(char *str,char a);

int main()
{
    int i,j, char_exists,substring;
    char string1[] = "jrsfahamfsf";
    char string2[] = "ham";

    char_exists = first_char_compare(string1,string2[0]);


    if(!(char_exists<0))
    {
        j=char_exists;

        for(i=0;string2[i]!='\0';i++)
        {
            for(;string1[j]!='\0';j++)
            {
                printf("%c\t%c\n",string2[i],string1[j]);
                if(string1[i]==string2[j])
                {
                    substring = 1;
                    printf("matches\n");
                    break;
                }
                else
                {
                    printf("doesn't match\n");
                    substring = 0;
                }
            }

            if(substring==0)
                break;

            j++;
        }

    }

    if(substring)
        printf("Is a substring\n");
    else
        printf("Not a substring\n");

    return 0;
}


int first_char_compare(char *str,char a)
{
/* Checks if the first character of the substring is in the main string.
 * If the character exists, it's index is returned. If it doesn't exist
 * -1 is returned.
 */
    int i;
    for(i=0;str[i]!='\0';i++)
    {
        if(a==str[i])
            return i;
    }
    return -1;
}

Upvotes: 0

Views: 103

Answers (1)

Paul Roub
Paul Roub

Reputation: 36458

In your loops, string2 is indexed by i, and string1 by j:

for (i = 0; string2[i] != '\0'; i++)
{
  for( ; string1[j] != '\0'; j++)
  {

But in your comparison, the indices are backwards:

if (string1[i] == string2[j])

correct that to:

if (string1[j] == string2[i])

Upvotes: 2

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