87 lines
2.4 KiB
Java
87 lines
2.4 KiB
Java
import java.util.*;
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/**
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* Model a 1D elementary cellular automaton.
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*
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* @author David J. Barnes and Michael Kölling
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* @version 2016.02.29 - version 3
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*/
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public class Automaton
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{
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// The number of cells.
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private final int numberOfCells;
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// The state of the cells.
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private int[] state;
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/**
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* Create a 1D automaton consisting of the given number of cells.
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* @param numberOfCells The number of cells in the automaton.
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*/
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public Automaton(int numberOfCells)
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{
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this.numberOfCells = numberOfCells;
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// Allow an extra element to avoid 'fencepost' errors.
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state = new int[numberOfCells + 1];
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// Seed the automaton with a single 'on' cell.
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state[numberOfCells / 2] = 1;
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}
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/**
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* Print the current state of the automaton.
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*/
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public void print()
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{
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for(int cellValue : state) {
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System.out.print(cellValue == 1 ? "*" : " ");
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}
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System.out.println();
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}
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/**
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* Update the automaton to its next state.
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*/
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public void update()
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{
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// Build the new state in a separate array.
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int[] nextState = new int[state.length];
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// Use 0 for the non-existent value to the left of
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// the first cell.
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int left = 0;
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int center = state[0];
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for(int i = 0; i < numberOfCells; i++) {
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int right = state[i + 1];
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nextState[i] = calculateNextState(left, center, right);
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left = center;
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center = right;
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}
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state = nextState;
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}
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/**
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* Reset the automaton.
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*/
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public void reset()
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{
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Arrays.fill(state, 0);
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// Seed the automaton with a single 'on' cell in the middle.
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state[numberOfCells / 2] = 1;
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}
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/**
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* Calculate the next state of the center cell
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* given current left, center and right cell
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* values.
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* This implements Wolfram code 110.
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* @see https://en.wikipedia.org/wiki/Wolfram_code
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* @param left The state of the cell to the left of center.
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* @param center The state of the center cell.
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* @param right The state of the cell to the right of center.
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* @return The new value of center (0 or 1).
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*/
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private int calculateNextState(int left, int center, int right)
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{
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return (center + right + center * right + left * center * right) % 2;
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}
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}
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