Operators Solution in C Programming

This Page Contains the Solution in C Programming Language for the Day 2 : Operators, Code Challange of the HackerRank 30 Days of Code.

#include <assert.h>
#include <ctype.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();
char* ltrim(char*);
char* rtrim(char*);

double parse_double(char*);
int parse_int(char*);

/*
 * Complete the 'solve' function below.
 *
 * The function accepts following parameters:
 *  1. DOUBLE meal_cost
 *  2. INTEGER tip_percent
 *  3. INTEGER tax_percent
 */

void solve(double meal_cost, int tip_percent, int tax_percent) 
{
    double tip=meal_cost*tip_percent/100;
    double tax=meal_cost*tax_percent/100;
    int totalCost=(int)round(meal_cost+tip+tax);    
    printf("%d",totalCost);
}

int main()
{
    double meal_cost = parse_double(ltrim(rtrim(readline())));

    int tip_percent = parse_int(ltrim(rtrim(readline())));

    int tax_percent = parse_int(ltrim(rtrim(readline())));

    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;
        }

        alloc_length <<= 1;

        data = realloc(data, alloc_length);

        if (!data) {
            data = '\0';

            break;
        }
    }

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

        data = realloc(data, data_length);

        if (!data) {
            data = '\0';
        }
    } else {
        data = realloc(data, data_length + 1);

        if (!data) {
            data = '\0';
        } else {
            data[data_length] = '\0';
        }
    }

    return data;
}

char* ltrim(char* str) {
    if (!str) {
        return '\0';
    }

    if (!*str) {
        return str;
    }

    while (*str != '\0' && isspace(*str)) {
        str++;
    }

    return str;
}

char* rtrim(char* str) {
    if (!str) {
        return '\0';
    }

    if (!*str) {
        return str;
    }

    char* end = str + strlen(str) - 1;

    while (end >= str && isspace(*end)) {
        end--;
    }

    *(end + 1) = '\0';

    return str;
}

double parse_double(char* str) {
    char* endptr;
    double value = strtod(str, &endptr);

    if (endptr == str || *endptr != '\0') {
        exit(EXIT_FAILURE);
    }

    return value;
}

int parse_int(char* str) {
    char* endptr;
    int value = strtol(str, &endptr, 10);

    if (endptr == str || *endptr != '\0') {
        exit(EXIT_FAILURE);
    }

    return value;
}