Homework in C - Help needed

[Ondrej_frajer]

Hey, I was accepted to the University for programming major, even though I basically never programmed anything in my life before, however my first homework here is to make a program in which I write 3 coordinates ([x, y]) and the program should be able to calculate 3 more coordinates so with one of the new coordinates and the 3 I wrote there, it would make a rectangle, or any of its special form (square, rhombus, parallelogram) and then the program should decide whether the newly formed tetragonal is square, etc. However, I need the program to work even when I fill in the coordinates in these forms

[ 5, 0 ]

or when it’s all written in one line only

[10.5, 10.5] [12.5, 10.5][10.5, 15e+0]

or when I write it like this [3,

4

])

but my program automatically says it’s incorrect input and I can’t figure out how to make that work, I even tried ai, but it didn’t help me neither, so any help from a more experienced programmer would be greatly appreciated. Everything else should work just fine. I hope that my problem is understandable as English isn’t my first language

Here is the part of my program, where I fill in the coordinates:

"Bod A" means coordinate A in my language and so on, and "Nespravny vstup" means incorrect input

int main(void) {
    double ax, ay, bx, by, cx, cy;
    double tolerance = 0.0000001;
    char input[100];

    printf("Bod A:\n");
    fgets(input, sizeof(input), stdin);
    if (sscanf(input, "[%lf, %lf]", &ax, &ay) != 2) {
        printf("Nespravny vstup.\n");
        return 1;
    }
    
      printf("Bod B:\n");
    fgets(input, sizeof(input), stdin);
    if (sscanf(input, "[%lf, %lf]", &bx, &by) != 2) {
        printf("Nespravny vstup.\n");
        return 1;
    }

    printf("Bod C:\n");
    fgets(input, sizeof(input), stdin);
    if (sscanf(input, "[%lf, %lf]", &cx, &cy) != 2) {
        printf("Nespravny vstup.\n");
        return 1;
    }

 

[simong1993]

Hey, congrats on getting into the programming major! I see what you're trying to do with your code, and I understand why it's giving you problems with the different input formats.

The issue is that your sscanf pattern ("[%lf, %lf]") is too strict, so it expects input exactly like [x, y]. This won't work with inputs that have extra spaces, newlines, or different formats.

To handle multiple input styles, you could try cleaning the input a bit before parsing it, removing any unnecessary spaces or newlines. Here's a suggestion:

1. Remove extra spaces, line breaks, and odd formatting.
2. Use a more flexible sscanf pattern.

Here's how you could tweak your input section:

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

void clean_input(char* input) {
    int i, j = 0;
    for (i = 0; input[i]; i++) {
        if (!isspace(input[i])) {  // Remove spaces, newlines
            input[j++] = input[i];
        }
    }
    input[j] = '\0';
}

int main(void) {
    double ax, ay, bx, by, cx, cy;
    char input[100];

    printf("Bod A:\n");
    fgets(input, sizeof(input), stdin);
    clean_input(input);
    if (sscanf(input, "[%lf,%lf]", &ax, &ay) != 2) {
        printf("Nespravny vstup.\n");
        return 1;
    }

    printf("Bod B:\n");
    fgets(input, sizeof(input), stdin);
    clean_input(input);
    if (sscanf(input, "[%lf,%lf]", &bx, &by) != 2) {
        printf("Nespravny vstup.\n");
        return 1;
    }

    printf("Bod C:\n");
    fgets(input, sizeof(input), stdin);
    clean_input(input);
    if (sscanf(input, "[%lf,%lf]", &cx, &cy) != 2) {
        printf("Nespravny vstup.\n");
        return 1;
    }

    // Continue with the rest of your program
}

The clean_input function strips spaces, line breaks, and other unnecessary characters, so that your sscanf can work more smoothly. This should help you handle those different formats like the ones you mentioned.

Give that a try and see if it works better! Let me know if you run into more trouble.