Implement Custom strcmp function

Question

Problem: Implement Custom strcmp function. Solve this hands-on electronics task on EWskills.

Accepted Answer

#include 

int custom_strcmp(const char *a, const char *b) {
    int i = 0;
    while (a[i] != '\0' && b[i] != '\0') {
        if (a[i] != b[i]) {
            return a[i] - b[i];  // Return ASCII difference
        }
        i++;
    }
    return a[i] - b[i];  // One might be longer than the other
}

int main() {
    char a[101], b[101];
    fgets(a, sizeof(a), stdin);
    fgets(b, sizeof(b), stdin);

    // Remove newline
    int i = 0;
    while (a[i]) {
        if (a[i] == '
') { a[i] = '\0'; break; }
        i++;
    }
    i = 0;
    while (b[i]) {
        if (b[i] == '
') { b[i] = '\0'; break; }
        i++;
    }

    printf("%d", custom_strcmp(a, b));
    return 0;
}

What does strcmp() really do?

It walks through both strings character by character. If it finds a mismatch, it returns the difference of their ASCII values. If it finishes both strings and finds no mismatch, it returns 0.

Why it’s important in firmware?

Used for comparing commands ("READ" vs "SET")
Lexical comparisons matter in bootloaders, menu navigation, etc.
Often used where string.h is not available

Solution Logic

Loop through characters
If any character differs, return the difference
If strings end, compare the null terminator too ('\0' - 'x' = -x)

92. Implement Custom strcmp function