10_3

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

namespace _10_2
{
    class Triangle
    {
        private int a;
        private int b;
        private int c;

        public Triangle()
        {
        }

        public Triangle(int a, int b, int c)
        {
            if (((a + b) > c) && ((b + c) > a) && ((a + c) > b))
            {
                this.a = a;
                this.b = b;
                this.c = c;
            }
            else
            {
                this.a = 1;
                this.b = 1;
                this.c = 1;
                Console.WriteLine("Triangle with these sides {0}, {1}, {2} can not be create, it will create triangle with sides of unit!", a, b, c);
            }
        }

        //public Triangle(int a, int b, int c)
        //{
        //        this.a = a;
        //        this.b = b;
        //        this.c = c;

        //}

        public void LengthsOfTheSide()
        {
            Console.WriteLine("Length of the first side: {0}", a);
            Console.WriteLine("Length of the second side: {0}", b);
            Console.WriteLine("Length of the third side: {0}", c);
        }

        public int Perimeter()
        {
            return a + b + c;
        }

        public double Square()
        {
            double S;
            double p = ((double)(a + b + c)) / 2;
            S = Math.Sqrt(p * (p - a) * (p - b) * (p - c));
            return S;
        }

        public int A
        {
            get
            {
                return a;
            }

            set
            {
                if (((value + b) > c) && ((b + c) > value) && ((value + c) > b))
                    a = value;
                else Console.WriteLine("The side a can not be change");
            }
        }

        public int B
        {
            get
            {
                return b;
            }

            set
            {
                if (((a + value) > c) && ((value + c) > a) && ((a + c) > value))
                    b = value;
                else Console.WriteLine("The side b can not be change");
            }
        }

        public int C
        {
            get
            {
                return c;
            }

            set
            {
                if (((a + b) > value) && ((b + value) > a) && ((a + value) > b))
                    c = value;
                else Console.WriteLine("The side c can not be change");
            }
        }

        public bool IfTriangle
        {
            get
            {
                if (((a + b) > c) && ((b + c) > a) && ((a + c) > b))
                    return true;
                else return false;
            }
        }

        public int this[int i]
        {
            get
            {
                if (i == 0) return a;
                else if (i == 1) return b;
                else if (i == 2) return c;
                else
                {
                    Console.WriteLine("Inadmissible index!");
                    return -1;
                }
            }

            set
            {
                if (i == 0)
                {
                    if (((value + b) > c) && ((b + c) > value) && ((value + c) > b))
                    a = value;
                    else Console.WriteLine("The side [0] can not be change");
                }
                else if (i == 1)
                {
                    if (((a + value) > c) && ((value + c) > a) && ((a + c) > value))
                        b = value;
                    else Console.WriteLine("The side [1] can not be change");
                }
                else if (i == 2)
                {
                    if (((a + b) > value) && ((b + value) > a) && ((a + value) > b))
                        c = value;
                    else Console.WriteLine("The side [2] can not be change");
                }
                else Console.WriteLine("Inadmissible index!");
            }

        }

        public static Triangle operator ++(Triangle tmp)
        {
            tmp.a++;
            tmp.b++;
            tmp.c++;
            return tmp;
        }

        public static Triangle operator --(Triangle tmp)
        {
            tmp.a--;
            tmp.b--;
            tmp.c--;
            return tmp;
        }

        public static bool operator true(Triangle tmp)
        {
            if (tmp.IfTriangle)
                return true;
            else return false;
        }

        public static bool operator false(Triangle tmp)
        {
            if (!tmp.IfTriangle)
                return false;
            else return true;
        }

        public static Triangle operator *(Triangle tmp, int x)
        {
            tmp.a *= x;
            tmp.b *= x;
            tmp.c *= x;
            return tmp;
        }
    }
}

 class Program
    {
        static void Main(string[] args)
        {
            Triangle first = new Triangle(4, 2, 5);
            Triangle second = new Triangle(3, 4, 5);
            Triangle third = new Triangle(1, 2, 3);

            first.LengthsOfTheSide();
            Console.WriteLine("Perimetere of the first Triangle is: {0}", first.Perimeter());
            Console.WriteLine("Square of the first Triangle is: {0,0}", first.Square());
            first.Square();
            first.A = 6;
            first.B = 0;
            first.C = 6;
            first.LengthsOfTheSide();
            first[0] = 9;
            first[1] = 12;
            first[2] = 7;
            first.LengthsOfTheSide();
            first++;
            first.LengthsOfTheSide();
            second--;
            second.LengthsOfTheSide();
            if (first) Console.WriteLine("Треугольник существует");
            else Console.WriteLine("Треугольник не существует");
            if (third) Console.WriteLine("Треугольник существует");
            else Console.WriteLine("Треугольник  не существует");
            Triangle four = second * 3;
            four.LengthsOfTheSide();
        }