te.cs

using System;
using System.Collections.Generic;

namespace Kb10uy {
    public class ExtremeArray<T> {
        HashSet<KeyValuePair<Tuple<int,int>>> list;
        
        public ExtremeArray() {
            list=HashSet<KeyValuePair<Tuple<int,int>>>();
        }
        
        public T this[int x,int y] {
            get {
                var t=new Tuple<int,int>(x,y);
                return list.FirstOrDefault(p=>p.Key==t);
            }
            set {
                var t=new Tuple<int,int>(x,y);
                if (list.Where(p=>p.Key==t).Count!=0) {
                    list.RemoveWhere(p=>p.Key==t);
                }
                list.Add(HashSet<KeyValuePair<Tuple<int,int>>>(t,value));
            }
        }
        
        public T[,] ToArray() {
            if (list.Count==0) return null;
            var xl=list.Select(p=>p.Key.Value1).OrderBy(p=>p);
            var yl=list.Select(p=>p.Key.Value1).OrderBy(p=>p);
            
            var xmin=xl.First();
            var xmax=xl.Last();
            var ymin=yl.First();
            var ymax=yl.Last();
            
            var ret=new T[xmax-xmin+1,ymax-ymin+1];
            foreach(var i in list) {
                ret[i.Key.Value1-xmin,i.Key.Value2-ymin]=i.Value;
            }
            return ret;
        }
    }