順列 C#

順列 C#

using System;
using System.Collections.Generic;

namespace Permutation
{
    class Program
    {
        static void Main(string[] args)
        {
            new Program();
        }

        public Program()
        {
            List<int> data = new List<int> { 1, 2, 3, 4 };
            List<List<int>> perm = GetPermutation(data);
            foreach (List<int> p in perm) {
                Console.WriteLine(string.Join(",", p));
            }
        }

        private List<List<int>> GetPermutation(List<int> data)
        {
            List<List<int>> perm = new List<List<int>>();
            if (data.Count == 0) {
                perm.Add(data);
                return perm;
            }

            for (int i = 0; i < data.Count; i++) {
                int head = data[i];

                List<int> dataCopy = new List<int>(data);
                dataCopy.RemoveAt(i);
                List<List<int>> childPerm = GetPermutation(dataCopy);
                foreach (List<int> child in childPerm) {
                    child.Insert(0, head);
                    perm.Add(child);
                }
            }
            return perm;
        }
    }
}