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117 lines
3.1 KiB
Java
117 lines
3.1 KiB
Java
/*
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* WorldEdit, a Minecraft world manipulation toolkit
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* Copyright (C) sk89q <http://www.sk89q.com>
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* Copyright (C) WorldEdit team and contributors
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*
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* This program is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <https://www.gnu.org/licenses/>.
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*/
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package com.sk89q.worldedit.util;
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import java.util.Optional;
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import java.util.function.Function;
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import static com.google.common.base.Preconditions.checkNotNull;
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/**
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* Returns the best choice given a weighting function and a target weight.
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*
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* <p>A function must be supplied that returns a numeric score for each
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* choice. The function can return null to mean that the choice should
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* not be considered.</p>
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*
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* @param <T> the type of choice
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*/
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public class WeightedChoice<T> {
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private final Function<T, ? extends Number> function;
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private final double target;
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private double best;
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private T current;
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/**
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* Create a new instance.
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*
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* @param function a function that assigns a score for each choice
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* @param target the target score that the best choice should be closest to
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*/
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public WeightedChoice(Function<T, ? extends Number> function, double target) {
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checkNotNull(function);
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this.function = function;
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this.target = target;
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}
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/**
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* Consider the given object.
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*
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* @param object the choice
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*/
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public void consider(T object) {
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checkNotNull(object);
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Number value = checkNotNull(function.apply(object));
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double distance = Math.abs(target - value.doubleValue());
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if (current == null || distance <= best) {
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best = distance;
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current = object;
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}
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}
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/**
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* Get the best choice.
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*
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* @return the best choice
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*/
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public Optional<Choice<T>> getChoice() {
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if (current != null) {
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return Optional.of(new Choice<>(current, best));
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} else {
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return Optional.empty();
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}
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}
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/**
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* A tuple of choice and score.
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*
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* @param <T> the choice type
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*/
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public static class Choice<T> {
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private final T object;
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private final double value;
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private Choice(T object, double value) {
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this.object = object;
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this.value = value;
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}
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/**
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* Get the chosen value.
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*
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* @return the value
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*/
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public T getValue() {
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return object;
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}
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/**
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* Get the score.
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*
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* @return the score
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*/
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public double getScore() {
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return value;
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}
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}
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}
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