[C#/COMMON] 순열(Permutation) 구하기

TestProject.zip

다운로드

▶ MainForm.cs

using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Linq;
using System.Windows.Forms;

namespace TestProject
{
    /// <summary>
    /// 메인 폼
    /// </summary>
    public partial class MainForm : Form
    {
        //////////////////////////////////////////////////////////////////////////////////////////////////// Constructor
        ////////////////////////////////////////////////////////////////////////////////////////// Public

        #region 생성자 - MainForm()

        /// <summary>
        /// 생성자
        /// </summary>
        public MainForm()
        {
            InitializeComponent();

            #region 이벤트를 설정한다.

            this.generateButton.Click += generateButton_Click;

            #endregion
        }

        #endregion

        //////////////////////////////////////////////////////////////////////////////////////////////////// Method
        ////////////////////////////////////////////////////////////////////////////////////////// Private
        //////////////////////////////////////////////////////////////////////////////// Event

        #region 생성 버튼 클릭시 처리하기 - generateButton_Click(sender, e)

        /// <summary>
        /// 생성 버튼 클릭시 처리하기
        /// </summary>
        /// <param name="sender">이벤트 발생자</param>
        /// <param name="e">이벤트 인자</param>
        private void generateButton_Click(object sender, EventArgs e)
        {
            string[] itemArray = itemTextBox.Text.Split(' ');

            List<List<string>> resultList = GetPermutationList<string>(itemArray.ToList());

            this.permutationListBox.Items.Clear();

            foreach(List<string> result in resultList)
            {
                this.permutationListBox.Items.Add(string.Join(" ", result.ToArray()));
            }

            long permutationCount = GetPermutationCount(itemArray.Length);

            this.permutationCountTextBox.Text = permutationCount.ToString();

            Debug.Assert(this.permutationListBox.Items.Count == permutationCount);
        }

        #endregion

        //////////////////////////////////////////////////////////////////////////////// Function

        #region 항목 바꿔넣기 - PermuteItem<T>(itemList, selectionArray, currentArray, resultList, nextPosition)

        /// <summary>
        /// 항목 바꿔넣기
        /// </summary>
        /// <typeparam name="T">항목 타입</typeparam>
        /// <param name="itemList">항목 리스트</param>
        /// <param name="selectionArray">선택 배열</param>
        /// <param name="currentArray">현재 배열</param>
        /// <param name="resultList">결과 리스트</param>
        /// <param name="nextPosition">다음 위치</param>
        private void PermuteItem<T>(List<T> itemList, bool[] selectionArray, T[] currentArray, List<List<T>> resultList, int nextPosition)
        {
            if(nextPosition == itemList.Count)
            {
                resultList.Add(currentArray.ToList());
            }
            else
            {
                for(int i = 0; i < itemList.Count; i++)
                {
                    if(!selectionArray[i])
                    {
                        selectionArray[i] = true;

                        currentArray[nextPosition] = itemList[i];

                        PermuteItem<T>(itemList, selectionArray, currentArray, resultList, nextPosition + 1);

                        selectionArray[i] = false;
                    }
                }
            }
        }

        #endregion
        #region 순열 리스트 구하기 - GetPermutationList<T>(itemList)

        /// <summary>
        /// 순열 리스트 구하기
        /// </summary>
        /// <typeparam name="T">항목 타입</typeparam>
        /// <param name="itemList">항목 리스트</param>
        /// <returns>순열 리스트</returns>
        private List<List<T>> GetPermutationList<T>(List<T> itemList)
        {
            T[] currentArray = new T[itemList.Count];

            bool[] selectionArray = new bool[itemList.Count];

            List<List<T>> resultList = new List<List<T>>();

            PermuteItem<T>(itemList, selectionArray, currentArray, resultList, 0);

            return resultList;
        }

        #endregion
        #region 순열 카운트 구하기 - GetPermutationCount(itemCount)

        /// <summary>
        /// 순열 카운트 구하기
        /// </summary>
        /// <param name="itemCount">항목 카운트</param>
        /// <returns>순열 카운트</returns>
        private long GetPermutationCount(long itemCount)
        {
            long result = 1;

            for(int i = 2; i <= itemCount; i++)
            {
                result *= i;
            }

            return result;
        }

        #endregion
    }
}