Phone Call

• first minute of a call costs min1 cents,
• each minute from the 2nd up to 10th (inclusive) costs min2_10 cents
• each minute after 10th costs min11 cents.

You have s cents on your account before the call. What is the duration of the longest call (in minutes rounded down to the nearest integer) you can have?

Example

For min1 = 3, min2_10 = 1, min11 = 2, and s = 20, the output should be

phone_call(min1, min2_10, min11, s) = 14

Here's why:

• the first minute costs 3 cents, which leaves you with 20 - 3 = 17 cents;
• the total cost of minutes 2 through 10 is 1 * 9 = 9, so you can talk 9 more minutes and still have 17 - 9 = 8 cents;
• each next minute costs 2 cents, which means that you can talk 8 / 2 = 4 more minutes.

Thus, the longest call you can make is 1 + 9 + 4 = 14 minutes long.

Solution

PYTHON

def phone_call(min1, min2_10, min11, s):
    mins = 0
    cost = 0

    while s > 0:
        mins += 1  # add one minute for each loop

        if mins == 1:  # 1st minute
            cost = min1
        elif mins == 2:  # 2nd to 10th minutes
            cost = min2_10
        elif mins >= 11:  # 11th minute onwards
            cost = min11

        s -= cost

        if s < 0:
            mins -= 1

    return mins


print(phone_call(10, 1, 2, 2))