C++ Coding Test Course, Sorting Numbers 1

Hello! In this lecture, we will cover the coding test problem “Sorting Numbers 1” using C++. This problem is a good foundation for sorting algorithms and allows us to compare the efficiency of various algorithms. We will examine the process of solving the problem step by step.

Problem Description

The problem is as follows:

Given N numbers, sort them in ascending order and print them.
(The integer N is between 1 and 1,000,000.)

Input example:

5
5
3
2
4
1

Output example:

1
2
3
4
5

Problem Analysis

This problem serves as a fundamental problem for sorting algorithms, where you simply need to sort and print the given numbers. It is ideal to use an efficient algorithm with a time complexity of O(N log N). The most commonly used sorting algorithms include Quick Sort, Merge Sort, and Heap Sort. In this problem, we can conveniently use the `std::sort` function from C++’s STL (Standard Template Library) to solve the problem easily.

Solve Process

1. Input Processing

First, we need to decide how to handle the input. In C++, we can use cin to read numbers from standard input. We will first input the number of values and then read the numbers into a vector.

2. Selecting a Sorting Algorithm

There are various sorting algorithms mentioned above, but it’s most convenient to use the std::sort function from C++ STL. This function internally uses the Quick Sort algorithm, providing an average performance of O(N log N).

3. Outputting the Sorted Result

To print the sorted results, we need to use a loop again. Since we need to line break with each printed number, we can utilize cout.

4. Code Implementation

Based on the above contents, let’s write the full code.

#include 
#include 
#include  // Include required for std::sort

using namespace std;

int main() {
    int N;
    cin >> N; // Input the number of values

    vector numbers(N); // Declare vector to store the numbers

    // Input the numbers
    for (int i = 0; i < N; i++) {
        cin >> numbers[i];
    }

    // Sort in ascending order
    sort(numbers.begin(), numbers.end());

    // Output the sorted numbers
    for (int i = 0; i < N; i++) {
        cout << numbers[i] << endl;
    }

    return 0;
}

Code Explanation

Let’s examine the code line by line:

• #include <iostream>: Library for input and output.
• #include <vector>: Library for using dynamic arrays.
• #include <algorithm>: Library for using STL algorithm functions.
• using namespace std;: Added to use the std namespace.
• int N;: Declares a variable to store the number of values.
• vector numbers(N);: Declares a vector to store N integers.
• cin: Used to receive input from the user for N numbers.
• sort(numbers.begin(), numbers.end());: Sorts the numbers in the vector in ascending order.
• cout: Outputs the sorted results.

Test Cases

Now that we have written the code, we will run it with various test cases. Below are some examples.

Example 1

Input:

5
5
3
2
4
1

Output:

1
2
3
4
5

Example 2

Input:

10
9
8
7
6
5
4
3
2
1
0

Output:

0
1
2
3
4
5
6
7
8
9

Example 3

Input:

3
1
1
1

Output:

1
1
1

Performance Analysis

Now let’s analyze the performance of the algorithm. std::sort has an average performance of O(N log N). Thus, even in cases where we input integers within the range of 1 to 1,000,000, it will operate quickly enough. While various sorting algorithms can also be used, std::sort is the most suitable for meeting the problem’s requirements.

Conclusion

In this lecture, we covered the “Sorting Numbers 1” problem using C++. We learned the basics of sorting as well as how to utilize STL. In the next lecture, we will explore more complex data structures and algorithms. Thank you!