pvjc25/du2/program.c

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

#define LINE_SIZE 100

// Function to safely read a double value
int read_double(double *value, int coef_index) {
    char line[LINE_SIZE];
    
    if (fgets(line, LINE_SIZE, stdin) == NULL) {
        return 0; // Error while reading
    }
    
    // Remove the newline character
    line[strcspn(line, "\r\n")] = 0;
    
    // Check if the line is empty
    if (strlen(line) == 0) {
        return 0;
    }
    
    char *endptr;
    *value = strtod(line, &endptr);
    
    // If no number was read or there are invalid characters
    if (endptr == line || *endptr != '\0') {
        return -1;  // Indicate error
    }
    
    return 1;
}

int main() {
    double x;
    
    // Read the value of x with special error message for invalid input
    int status = read_double(&x, 1);
    if (status == -1) {
        printf("Nepodarilo sa nacitat zaklad x\n");
        return 1;
    }
    if (status == 0) {
        return 1; // Exit if no input is provided
    }

    double coef;
    double result = 0;
    int coef_count = 0; // Start counting coefficients from 0

    // Loop to read coefficients
    while (1) {
        coef_count++;  // Increase coefficient index for each input
        status = read_double(&coef, coef_count);
        
        if (status == -1) {
            return 0;  // Exit program if there's invalid input
        }
        
        if (status == 0) {
            if (coef_count == 1) { // If no coefficient is provided for x^0
                return 1;
            }
            break;
        }
        
        result = result * x + coef;  // Apply Horner's method for polynomial evaluation
    }

    // Print the result
    printf("Vysledok je: %.2f\n", result);
    return 0;
}