Day 2: Operators

#include <assert.h>
#include <limits.h>
#include <math.h>
#include <stdbool.h>
#include <stddef.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

char* readline();

// Complete the solve function below.
void solve(double meal_cost, int tip_percent, int tax_percent) {
double Tip,Tax;
Tip = meal_cost*((double)tip_percent/100);
Tax = meal_cost*((double)tax_percent/100);
double TotalCost = meal_cost + Tip + Tax;
double h=round(TotalCost);
printf("%.0lf",h);
}

int main()
{
    char* meal_cost_endptr;
    char* meal_cost_str = readline();
    double meal_cost = strtod(meal_cost_str, &meal_cost_endptr);

    if (meal_cost_endptr == meal_cost_str || *meal_cost_endptr != '\0') { exit(EXIT_FAILURE); }

    char* tip_percent_endptr;
    char* tip_percent_str = readline();
    int tip_percent = strtol(tip_percent_str, &tip_percent_endptr, 10);

    if (tip_percent_endptr == tip_percent_str || *tip_percent_endptr != '\0') { exit(EXIT_FAILURE); }

    char* tax_percent_endptr;
    char* tax_percent_str = readline();
    int tax_percent = strtol(tax_percent_str, &tax_percent_endptr, 10);

    if (tax_percent_endptr == tax_percent_str || *tax_percent_endptr != '\0') { exit(EXIT_FAILURE); }

    solve(meal_cost, tip_percent, tax_percent);

    return 0;
}

char* readline() {
    size_t alloc_length = 1024;
    size_t data_length = 0;
    char* data = malloc(alloc_length);

    while (true) {
        char* cursor = data + data_length;
        char* line = fgets(cursor, alloc_length - data_length, stdin);

        if (!line) { break; }

        data_length += strlen(cursor);

        if (data_length < alloc_length - 1 || data[data_length - 1] == '\n') { break; }

        size_t new_length = alloc_length << 1;
        data = realloc(data, new_length);

        if (!data) { break; }

        alloc_length = new_length;
    }

    if (data[data_length - 1] == '\n') {
        data[data_length - 1] = '\0';
    }

    data = realloc(data, data_length);

    return data;
}