Python Coding Test Course, Calculating ATM Withdrawal Time

You are now preparing for job applications and coding tests. In this course, we will learn how to develop efficient problem-solving skills by solving a problem that calculates ATM withdrawal times using Python.

Problem Definition

The bank’s ATM processes withdrawal requests from multiple people. Each request is generated at a specific time, and we need to calculate the time it takes to process the requests. The problem is as follows:

Write a simulation of withdrawal requests being processed. The requests occur when n customers line up at the ATM, and the time each customer takes to withdraw money is given. You need to output the total time it takes to process all customers' withdrawal requests.

Input:
- The first line contains the number of customers n. (1 ≤ n ≤ 1000)
- The second line contains the time each customer takes to withdraw money, separated by spaces.

Output:
- Print the total time taken to process all customers' requests.

Example Input/Output

Input:

5
3 1 4 3 2

Output:

32

Problem Analysis

When a customer requests a withdrawal at the ATM, each customer is processed one at a time in the order they arrive. During this time, other customers must wait until one customer’s request is completed. Therefore, to calculate the time taken to process all customers’ withdrawal requests, you need to go through the following steps:

  1. Calculate the cumulative time using the withdrawal times of each customer.
  2. Include the waiting times of each customer to find the total time taken.

Algorithm Design

To solve this problem, you can design the following algorithm:

  1. Store the number of customers n and the withdrawal times of each customer in a list.
  2. Add the withdrawal time of the first customer to the cumulative time total.
  3. For each subsequent customer, add the current customer’s withdrawal time to the cumulative time based on the time of the previous customer.
  4. Sum the total time for all customers and print the result.

Python Code Implementation

Let’s implement the Python code based on the above algorithm.

def calculate_total_withdraw_time(n, withdraw_times):
    total_time = 0
    for i in range(n):
        total_time += withdraw_times[i] * (n - i)
    return total_time

# Input values taken from stdin
n = int(input("Enter number of customers: "))
withdraw_times = list(map(int, input("Enter withdrawal times for each customer: ").split()))

# Calculate total withdrawal time
total_time = calculate_total_withdraw_time(n, withdraw_times)
print("Total time taken to process all customers' requests:", total_time)

Code Explanation

Let’s examine each part of the code:

  • Function Definition: The calculate_total_withdraw_time function takes the number of customers n and the withdrawal times as arguments and calculates the total withdrawal time.
  • Total Time Calculation: After initializing the total_time variable, a loop is used to incrementally calculate the total time based on each customer’s withdrawal time.
  • Input Handling: It receives the number of customers and withdrawal times as input and converts them into a list to pass to the function.
  • Output: It prints the calculated total time.

Complexity Analysis

The code runs in a single loop for the number of customers n to calculate the total withdrawal time, so the time complexity is O(n). The space complexity is O(1) as it only uses constants outside the input list.

Conclusion

In this course, we studied how to analyze problems and design algorithms in Python programming through a problem that calculates ATM withdrawal times. Such problems often appear in actual coding tests, so it is important to practice sufficiently to develop problem-solving skills. Looking for additional practice problems and solutions is also a good approach.

I hope this has helped you in preparing for coding tests, and I look forward to encountering more algorithm problems in the next course!