65 lines
2.0 KiB
Java
65 lines
2.0 KiB
Java
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/*
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This is a Java Program to Implement Shoelace Algorithm. The shoelace formula, or shoelace algorithm, is a mathematical algorithm to determine the area of a simple polygon whose vertices are described by ordered pairs in the plane
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*/
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/**
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** Java Program to Implement Shoelace Algorithm
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**/
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import java.util.Scanner;
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/** Class Shoelace **/
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public class Shoelace
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{
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/** Function to calculate area **/
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public double area(int[][] arr)
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{
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int n = arr.length;
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/** copy initial point to last row **/
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arr[n - 1][0] = arr[0][0];
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arr[n - 1][1] = arr[0][1];
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double det = 0.0;
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/** add product of x coordinate of ith point with y coordinate of (i + 1)th point **/
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for (int i = 0; i < n - 1; i++)
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det += (double)(arr[i][0] * arr[i + 1][1]);
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/** subtract product of y coordinate of ith point with x coordinate of (i + 1)th point **/
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for (int i = 0; i < n - 1; i++)
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det -= (double)(arr[i][1] * arr[i + 1][0]);
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/** find absolute value and divide by 2 **/
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det = Math.abs(det);
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det /= 2;
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return det;
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}
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/** Main function **/
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public static void main (String[] args)
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{
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Scanner scan = new Scanner(System.in);
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System.out.println("Shoelace Algorithm Test\n");
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/** Make an object of Shoelace class **/
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Shoelace s = new Shoelace();
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/** Accept number of points **/
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System.out.println("\nEnter number of points");
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int n = scan.nextInt();
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int[][] arr = new int[n + 1][2];
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System.out.println("Enter "+ n +" x, y coordinates");
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for (int i = 0; i < n; i++)
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{
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arr[i][0] = scan.nextInt();
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arr[i][1] = scan.nextInt();
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}
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double area = s.area(arr);
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System.out.println("\nArea = "+ area);
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}
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}
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/*
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Enter number of points
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5
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Enter 5 x, y coordinates
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3 4
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5 11
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12 8
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9 5
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5 6
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Area = 30.0
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