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CSharp · Console

/Program.cs

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

namespace PerimeterAndAreaOfPolygon
{
    class Point
    {
        public double x;
        public double y;

        public Point(double X, double Y)
        {
            x = X;
            y = Y;
        }

        public double Distance(Point p2)
        {
            double x1 = this.x;
            double y1 = this.y;
            double x2 = p2.x;
            double y2 = p2.y;
            return Math.Sqrt(Math.Pow(x1 - x2, 2) + Math.Pow(y1 - y2, 2));
        }
    }
   
    class Polygon
    {
        List<Point> poly;
        int m;

        public Polygon(List<Point> polygon)
        {
            if (polygon.Count > 2)
            {
                this.poly = polygon;
                poly.Add(polygon[0]);
                m = poly.Count();
            }
            else
            {
                Console.WriteLine("Cannot make polygon with less than 3 points!");
            }
        }

        public double Perimeter()
        {
            double perimeter = 0;
            for (int i = 0; i < m-1; i++)
            {
                Point p1 = poly[i];
                Point p2 = poly[i + 1];
                perimeter += p1.Distance(p2);
            }
            return perimeter;
        }

        public double Area()
        {
            double left = 0;
            double right = 0;
            for (int i = 0; i < m-1; i++)
            {
                Point p1 = poly[i];
                Point p2 = poly[i+1];
                left += p1.x * p2.y;
                right += p2.x * p1.y;
            }
            return Math.Abs(left-right)/2;
        }
    }

    public class Program
    {
        public static void Main()
        {
            Console.WriteLine(@"Program that calculates the perimeter and the area of given polygon (not necessarily convex) 
consisting of n floating-point coordinates in the 2D plane.");
            Console.WriteLine("Write n = ");
            int n = int.Parse(Console.ReadLine());
            List<Point> listOfPoints = new List<Point>{};
            for (int i = 0; i < n; i++)
            {
                Console.WriteLine("Write coordinates of point {0}:", i + 1);
                string line = Console.ReadLine();
                string[] list = line.Split(' ');
                double x = double.Parse(list[0]);
                double y = double.Parse(list[1]);
                Point p = new Point(x, y);
                listOfPoints.Add(p);
            }
            Polygon polygon = new Polygon(listOfPoints);
            double perimeter = polygon.Perimeter();
            double area = polygon.Area();
            Console.WriteLine("The area is {0:0.00} and the perimeter is {1:0.00}.", area, perimeter);
        }
    }
}