[Stage 31] Deposit Profit

You have deposited a specific amount of dollars into your bank account. Each year your balance increases at the same growth rate. Find out how long it would take for your balance to pass a specific threshold with the assumption that you don’t make any additional deposits.

Example

For deposit = 100, rate = 20 and threshold = 170, the output should be depositProfit(deposit, rate, threshold) = 3.

Each year the amount of money on your account increases by 20%. It means that throughout the years your balance would be:

• year 0: 100;
• year 1: 120;
• year 2: 144;
• year 3: 172,8.
• Thus, it will take 3 years for your balance to pass the threshold, which is the answer.

Input/Output

• [execution time limit] 4 seconds (py3)

• [input] integer deposit

The initial deposit as a positive integer.

Guaranteed constraints: 1 ≤ deposit ≤ 100.

• [input] integer rate

The rate of increase. Each year the balance increases by the rate percent of the current sum.

Guaranteed constraints: 1 ≤ rate ≤ 100.

• [input] integer threshold

The target balance.

Guaranteed constraints: deposit < threshold ≤ 200.

• [output] integer

The number of years it would take to hit the threshold.

def depositProfit(deposit, rate, threshold):
    year = 0
    while deposit < threshold:
        deposit *= (1+rate/100)
        year += 1
    return year