问寻找重复

EN

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Practice
{
    #region FindDuplicate
    class FindDuplicate
    {
        private int[] input;
        private List<int> dupList;
        private IEnumerable<int> dupes;

        public FindDuplicate(int[] input)
        {
            this.input = input;
        }


        /**
         * This is a more advanced version of printing out the duplicates in the sense that we are using
         * SQL-Like statements in the form of Group, where, and select. If these were SQL it may look like:
         * SELECT * FROM INPUT s1
         * JOIN INPUT s2
         * ON s2.value = s1.value 
        */
        public FindDuplicate finderVariantTwo()
        {
            //Note how we do not need to sort the array, the grouping will do it for us.
            this.dupes = this.input.GroupBy(result => result)
                .Where(whereValueClause => whereValueClause.Count() > 1)
                .Select(indexValue => indexValue.Key);

            return this;
        }

        /**
         * This is the "naive" variant, and the one that first came to my mind. The idea here is simple: 
         * First, 
         */
        public FindDuplicate getDuplicates()
        {
            this.dupList = new List<int>();

            //for this, let us first sort the array to make it easier for the loop. 
            Array.Sort(this.input);

            for(int i = 0; i < input.Length; i++)
            {
                //this is to make sure we do not have an index out of bounds.
                int next = (i < input.Length-1) ? i+1 : input.Length - 1;

                if(input[i] == input[next] && !dupList.Contains(input[i]))
                {
                    dupList.Add(input[i]);
                }
            }

            return this;
        }


        public void getDuplicatesTwo()
        {
            String result = "Result => {";
            foreach (int i in this.dupes)
            {
                result += i + ",";
            }
            result += "}";
            Console.WriteLine(result);
        }

        public void printResultVariantOne()
        {
            String result = "Result => {";
            foreach(int i in this.dupList)
            {
                result += i + ",";
            }
            result += "}";
            Console.WriteLine(result);
        }
        #endregion
    }

    class TestFindDuplicates
    {
        static void Main(string[] args)
        {
            int[] input = { 2, 3, 2, 4, 5, 5, 1, 10, 3, 10, 9, 9 };

            FindDuplicate find = new FindDuplicate(input);

            find.getDuplicates().printResultVariantOne();

            Console.WriteLine("\n");

            find.getDuplicatesTwo().printResultVariantTwo();

            //to stop the window from closing as soon as it finishes running
            Console.ReadKey();
        }
    }
}