91 lines
2.9 KiB
Java
91 lines
2.9 KiB
Java
////////////////////////////////////////
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// Programming project code
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// UniBw M, 2022, 2023, 2024
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// www.unibw.de/inf2
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// (c) Mark Minas (mark.minas@unibw.de)
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////////////////////////////////////////
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package pp.util;
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import java.util.ArrayList;
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import java.util.Collections;
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import java.util.HashSet;
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import java.util.List;
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import java.util.Set;
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/**
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* A class with auxiliary functions.
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*/
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public class Util {
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private Util() { /* do not instantiate */ }
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/**
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* Calculates and returns the area of a polygon defined by a list of points, using the shoelace formula.
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* The result is positive if the sequence of vertices is in clockwise order, and negative
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* otherwise.
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*
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* @param points A list of positions that define the vertices of the polygon in planar coordinates.
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* @return The calculated area of the polygon.
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*/
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public static float getArea(List<? extends Position> points) {
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float sum = 0;
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Position prev = getLast(points);
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for (var next : points) {
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sum += prev.getX() * next.getY() - next.getX() * prev.getY();
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prev = next;
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}
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return 0.5f * sum;
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}
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/**
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* Returns the last element of the given list.
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*
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* @param list the list from which to retrieve the last element
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* @param <T> the type of elements in the list
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* @return the last element of the list
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* @throws IndexOutOfBoundsException if the list is empty
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*/
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public static <T> T getLast(List<T> list) {
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return list.get(list.size() - 1);
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}
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/**
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* Reverses the order of elements in the given list.
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*
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* @param list the list to be reversed
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* @param <T> the type of elements in the list
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* @return a new list with elements in reversed order
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*/
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public static <T> List<T> reverse(List<T> list) {
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final List<T> reversed = new ArrayList<>(list);
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Collections.reverse(reversed);
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return reversed;
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}
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/**
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* Creates a copy of the given list.
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*
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* @param list the list to be copied, may be null
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* @param <T> the type of elements in the list
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* @return a new list containing the elements of the original list, or null if the original list is null
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*/
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public static <T> List<T> copy(List<T> list) {
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return list == null ? null : new ArrayList<>(list);
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}
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/**
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* Adds an element to a set and returns a new set containing the original elements and the new element.
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*
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* @param set the original set, must not be null
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* @param element the element to be added to the set
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* @param <T> the type of elements in the set
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* @param <E> the type of the element being added, must extend T
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* @return a new set containing the original elements and the new element
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*/
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public static <T, E extends T> Set<T> add(Set<T> set, E element) {
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final Set<T> newSet = new HashSet<>(set);
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newSet.add(element);
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return newSet;
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}
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}
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