why the outputs for these two equivalent functions are different?-CodePudding

I tried to solve this problem using two approaches. The first one calculates the rent from the bottom-up while the second one does it from the top-down. Unfortunately, I cannot identify what is causing them to return different outputs instead of the same one.

Here is the question: From a renter's monthly income, the landlord gets to keep 5% of the first $0 to $9999 10% of the remaining $10k to $19999 15% of the remaining $20k to $49999 20% of the remaining $50k to $99999 30% of the remaining $100000 and above. Find out how much rent the renter will have to pay this month if their monthly income was $23,000.

def calculate_rent_1(renter_salary):
    rent = 0
    if renter_salary > 0:
        if renter_salary <= 9999:
            return 0.05 * renter_salary
        else:
            rent  = 0.05 * 9999
            renter_salary -= 9999

    if renter_salary > 9999:
        if renter_salary <= 19999:
            return rent   0.1 * renter_salary
        else:
            rent  = 0.1 * 9999
            renter_salary -= 9999
    
    if renter_salary > 19999:
        if renter_salary <= 49999:
            return rent   0.15 * renter_salary
        else:
            rent  = 0.15 * 29999
            renter_salary -= 29999
    
    if renter_salary > 49999:
        if renter_salary <= 99999:
            return rent   0.2 * renter_salary
        else:
            rent  = 0.2 * 49999
            renter_salary -= 49999
    
    if renter_salary > 99999:
        return rent   0.3 * renter_salary


def calculate_rent_2(renter_salary):
    if not renter_salary: return 0
    rent = 0
    if 100000 <= renter_salary:
        rent  = 0.3 * (renter_salary - 100000)
        renter_salary = 99999
    if 50000 <= renter_salary:
        rent  = 0.2 * (renter_salary - 50000)
        renter_salary = 49999
    if 20000 <= renter_salary:
        rent  = 0.15 * (renter_salary - 20000)
        renter_salary = 19999
    if 10000 <= renter_salary:
        rent  = 0.1 * (renter_salary - 10000)
        renter_salary = 9999
    if 0 < renter_salary:
        rent  = 0.05 * renter_salary
    
    return rent

print("Output from calculate_rent_1:", calculate_rent_1(23000)) # output: 1800.0500000000002
print("Output from calculate_rent_2:", calculate_rent_2(23000)) # output: 1949.8500000000001

CodePudding user response：

I presume you realize the second function is the correct one. Your problem is in the first function:

    rent = 0
    if renter_salary > 0:
        if renter_salary <= 9999:
            return 0.05 * renter_salary
        else:
            rent  = 0.05 * 9999
            renter_salary -= 10000

    print( rent, renter_salary)
    if renter_salary > 9999:
        if renter_salary <= 19999:   ##<<<<<<
            return rent   0.1 * renter_salary
        else:
            rent  = 0.1 * 9999
            renter_salary -= 10000

In the marked line, you're checking for salary <= 19999, but by this time you have already subtracted off the initial 10,000. This needs to check for 9999. The same repeats in the other clauses.

CodePudding user response：

Here is my answer after correcting my approach for calculate_rent_1 and modifying the upper bounds for calculate_rent_2. The reason for the latter is that if the renter_salary is $100,000, I would want to include as part of the rent 0.3% of the $1 that is above $99,999.

def calculate_rent_1(renter_salary):
    if not renter_salary: return 0
    rent = 0

    if (renter_salary - 9999) <= 0:
        return 0.05 * rent
    
    rent  = 0.05 * 9999
    renter_salary -= 9999

    if (renter_salary - 9999) <= 0:
        return rent   0.1 * renter_salary
    
    rent  = 0.1 * 9999
    renter_salary -= 9999

    if (renter_salary - 29999) <= 0:
        return rent   0.15 * renter_salary
    
    rent  = 0.15 * 29999
    renter_salary -= 29999

    if (renter_salary - 49999) <= 0:
        return rent   0.2 * renter_salary
    
    rent  = 0.2 * 49999
    renter_salary -= 49999

    if renter_salary > 0:
        return rent   0.3 * renter_salary
    
    return rent

def calculate_rent_2(renter_salary):
    if not renter_salary: return 0
    rent = 0

    if 100000 <= renter_salary:
        rent  = 0.3 * (renter_salary - 99999)
        renter_salary = 99999

    if 50000 <= renter_salary:
        rent  = 0.2 * (renter_salary - 49999)
        renter_salary = 49999

    if 20000 <= renter_salary:
        rent  = 0.15 * (renter_salary - 19999)
        renter_salary = 19999

    if 10000 <= renter_salary:
        rent  = 0.1 * (renter_salary - 9999)
        renter_salary = 9999

    if 0 <= renter_salary:
        rent  = 0.05 * renter_salary
    
    return rent

print("Output from calculate_rent_1:", calculate_rent_1(23000)) # output: 1950.15
print("Output from calculate_rent_2:", calculate_rent_2(23000)) # output: 1950.1000000000001