Finding substring in string without using library function
<p>Below is the code template and under /* write your code here */ is my own code.
The template should be correct but there is sth wrong with my code.</p>

<p>My algorithm is to iterate through str until finding the null character.
Then compare each character, if they are the same then iterate through both str and sub, otherwise set continue to iterate through str and reset to the first character of substr.</p>

<pre><code>#include &lt;stdio.h&gt;
int findSubstring(char *str, char *substring);
int main()
{
    char str[40], substr[40];
    printf("Enter the string: ");
    gets(str);
    printf("Enter the substring: ");
    gets(substr);
    printf("findSubstring(): %d\n", findSubstring(str, substr));
    return 0;
}
int findSubstring(char *str, char *substr)
{
    /* write your code here */
    int i = 0, j = 0;
    while ((str[j] != '\0')||(substr[i] != '\0')) {
        if (substr[i] != str[j]) {
            j++;
            i = 0;
        }
        else {
            i++;
            j++;
        }
    }
    if (substr[i] == '\0')
        return 1;
    else
        return -1;
}
</code></pre>