计算字符串中 Substring 的出现次数

Question

My program is supposed to count in a string an entered string.

For example:

Enter a text: Hello World
Enter a string: llo
occurs 1 times in Hello World

Unfortunately, my program does not give me anything. Does anyone have a tip for me?

void aufgabe7(char string[MAX], char stringw[MAX]){
    printf("Enter a Text: \n");
    fgets(string, MAX, stdin);
    int i, j, len, len2;
    int count = 0;
    int count2 = 0;
    len = strlen(string);
    
    printf("Enter a string: \n");
    fgets(stringw, MAX, stdin);
    len2 = strlen(stringw);

    for (i = 0; i < len;)
    {
        j = 0;
        count = 0;
        while ((string[i] == stringw[j]))
        {
            count++;
            i++;
            j++;
        }
        if (count == len2)
        {
            count2++;
            count = 0;
        }
        else
            i++;
        
        
    }
    
    printf("%s occurs %d times in %s \n", stringw, count2, string);
    
}

void main (void){

    char data[MAX];
    task7(&data[0], &data[0]);

}

Answer 1

As commenter @Steve Summit noted, you are searching for a string read from fgets , which has a trailing newline. Normally, you would need to remove the newline from the input from fgets , otherwise it is part of the searched for string. The simplest way to do this is to call buffer[strcspn(buffer, "\n")] = '\0'; as documented in this question .

However, I feel the correct answer to this question is that there is a more idiomatic way of doing this with C than comparing char by char : using strstr with pointer arithmetic will work just as well and is cleaner to read:

char input[SIZE];
char search[SIZE];
size_t count = 0;

printf("Enter a phrase: ");
fgets(input, SIZE, stdin);
input[strcspn(input, "\n")] = '\0'; 
printf("\nEnter a sub-phrase: ");
fgets(search, SIZE, stdin);
search[strcspn(search, "\n")] = '\0';
char *p = input;
while((p = strstr(p, search)) != NULL)
{
    printf("Found occurrence of '%s' at position %td\n", search, (ptrdiff_t)(p - input));
    count++;
    p++;
}

printf("Found %zu occurrences of '%s'.\n", count, search);