python coding test course, picking up pebbles

In this post, we will explore problem-solving methods commonly encountered in Python coding tests through an algorithm problem called “Picking Up Pebbles.” We will define the problem, establish a solution strategy, and ultimately provide Python code.

Problem Description

You discovered pebbles while walking along the beach. Each pebble has a different weight. When picking up pebbles, you must pick up two pebbles at a time, and the maximum number you can pick is N.

Your goal is to calculate the minimum number of times you need to pick up to remove all the pebbles’ weights. Additionally, the weights of the pebbles you pick must be selected from those that have not been picked before.

Input Format

The input follows this format:

  • The first line contains the number of weights N.
  • The second line contains the weights of N.

The output should return the minimum number of times you need to pick up to remove all the pebbles’ weights.

Example

Input:
5
1 2 3 4 5

Output:
3

Problem Analysis

When picking the weights of the pebbles, we can pick two pebbles at a time, but we need to choose the weights we pick as diversely as possible. Therefore, to efficiently pick the given weights, we need to include all weights through the smallest number of picks.

Solution Strategy

This problem can be simply explained as a combination problem. Since we can pick two pebbles at a time with each pick, we need to consider half the number of weights. Counting the weights of each pebble and calculating the number of picks based on the count of weights is essential.

Algorithm Implementation

You can solve the problem based on the following algorithm:

  1. Read the number of weights N.
  2. Store each pebble’s weight in a list.
  3. Count the weights of the pebbles.
  4. Calculate the minimum number of picks by rounding up half the number of weights.

Python Code Implementation

The code below implements the above algorithm in Python:

import math

def min_pickups(weights):
    unique_weights = set(weights)
    return math.ceil(len(unique_weights) / 2)

# Taking input
N = int(input("Please enter the number of weights: "))
weights = list(map(int, input("Please enter the weights of the pebbles: ").split()))
result = min_pickups(weights)
print("Minimum number of picks required to remove all pebbles:", result)

Code Explanation

The provided code first defines the min_pickups function. This function calculates the number of unique pebble weights from the input, then returns the final result by rounding up half of that number.

In the main part, it takes user input to create a list containing the weights and passes this list to the min_pickups function to output the results.

Conclusion and Tips

In this tutorial, we learned problem-solving methods for Python coding tests through the “Picking Up Pebbles” problem. Algorithm problems often involve combinations and ordering, so when solving such problems, it’s essential to effectively count weights and construct combinations.

I hope to deepen my understanding of algorithms through various problems in the future. I will continue to provide useful problem-solving methods and coding tips next time as well. Thank you!