Sara Pesavento - Rdvark Blog

Operators

Posted by : Sara Pesavento at Jun 10, 2020

The objective of this challenge is to find the total cost of a meal given the mealCost, tipPercent, and taxPercent. The total cost of the meal, rounded to the nearest dollar, can be stored in the variable totalCost.

Sample Input:

12.00
20
8

Sample Output:

15  #12.00 + 12.00*(20/100) + 12.00*(8/100) = round(15.36) = 15

For this problem, HackerRank provides the user the following code and asks them to complete the solve function. The comments below help to explain these lines of code.

#!/bin/python3 
# a "shebang line" that defines where the interpreter is located 
# (lets the operating system know it's a python script)

import math  #imports math library which contains math functions like sqrt(x) or pow(x,y)
import os   #os library provides functions for interacting with the operating system
import random #random library allows you to generate random number samples
import re #re library provides functions to search a string for a match or pattern
import sys 
# sys library provides info on interaction with the host system (e.g. version, execution)

# This is the function they would like you to complete. It needs to calculate the total meal 
# cost given the parameters: meal_cost, tip_percent, tax_percent.
def solve(meal_cost, tip_percent, tax_percent):

if __name__ == '__main__':  
#__name__ is a built-in variable which is set to "__main__" if it is being run directly as 
# the main program, as it is here. Otherwise, if the module is imported, __name__ is set to the
# name of the current module. For example, if your file is called foo.py, if it's run as 
# the main program, then __name__ is set to "__main__". If it's imported, the main program 
# imports it as import foo, which is equivalent to setting __name__ = "foo"

    meal_cost = float(input()) 
    # takes a user input, converts it from a string to a float, stores it in meal_cost

    tip_percent = int(input())
    # takes a user input, converts it from a string to a integer, stores it in tip_percent

    tax_percent = int(input())
    # takes a user input, converts it from a string to a integer, stores it in tip_percent
    
    solve(meal_cost, tip_percent, tax_percent) 
    # calls the function (has the function run with the three arguments: 
    # meal_cost, tip_percent, tax_percent)

Inside the function, we just need to calculate the total cost as meal_cost + meal_cost(tip_percent/100) + meal_cost(tax_percent/100). With meal_cost = 12.00, tip_percent = 20, and tax_percent = 8, this generates 15.36, a float. Just converting to an integer will always round it down, rather than “to the nearest dollar”.

int(15.36)
int(15.89)

15
15

Instead, you can first round it to 0 decimal places using round(x,0)

round(15.36, 0)
round(15.89, 0)

15.0
16.0

Then convert the rounded float to an integer.

int(round(15.36, 0))
int(round(15.89, 0))

15
16

Sample Solution:

#!/bin/python3

import math
import os
import random
import re
import sys

# Complete the solve function below.
def solve(meal_cost, tip_percent, tax_percent):

    print(int(round(meal_cost + meal_cost*(tip_percent/100) + meal_cost*(tax_percent/100), 0)))

if __name__ == '__main__':
    meal_cost = float(input())

    tip_percent = int(input())

    tax_percent = int(input())

    solve(meal_cost, tip_percent, tax_percent)