Advent of Code 2016 Day 21 /u/Philboyd_Studge

Advent2016_21.java

import java.util.Collections;
import java.util.List;
import java.util.function.BiConsumer;

/**
 * @author /u/Philboyd_Studge on 12/20/2016.
 */
public class Advent2016_21 {
    
    enum Command {
        swap(Advent2016_21::swap),
        move(Advent2016_21::move),
        rotate_right(Advent2016_21::rotate_right),
        rotate_left(Advent2016_21::rotate_left),
        rotate_based(Advent2016_21::rotate_based),
        reverse(Advent2016_21::reverse);

        BiConsumer<Integer, Integer> func;

        Command(BiConsumer<Integer, Integer> func) { this.func = func; }
    }

    // for part 2 - number of left shifts to reverse 'rotate based on'
    final static int[] reverseLookup = { 1, 1, 6, 2, 7, 3, 0, 4 };

    static int findIndex(int c) {
        for (int i = 0; i < password.length; i++) {
            if (password[i] == (char) c) return i;
        }
        return -1;
    }

    static void swap(int x, int y) {
        if (x > 7) x = findIndex(x);
        if (y > 7) y = findIndex(y);
        char temp = password[x];
        password[x] = password[y];
        password[y] = temp;
    }


    static void move(int x, int y) {
        char temp = password[x];
        if (x < y) {
            rotate_left(x, y);
        } else {
            rotate_right(x, y);
        }
        password[y] = temp;
    }

    static void rotate_right(int x, int y) {
        if (y >= 0) {
            for (int i = x; i > y; i--) {
                swap(i, i - 1);
            }
        } else {
            for (int i = 0; i < x; i++) {
                for (int j = password.length - 1; j > 0; j--) {
                    swap(j, j - 1);
                }
            }
        }
    }

    static void rotate_left(int x, int y) {
        if (y >= 0) {
            for (int i = x; i < y; i++) {
                swap(i, i + 1);
            }
        } else {
            for (int i = 0; i < x; i++) {
                for (int j = 0; j < password.length - 1; j++) {
                    swap(j, j + 1);
                }
            }
        }
    }

    static void rotate_based(int x, int y) {
        int index = findIndex(x);
        rotate_right(1 + index +  (index >= 4 ? 1 : 0), -1);
    }

    static void reverse(int x, int y) {
        for (int i = 0; i <= (y - x)/2; i++) {
            swap(x + i, y - i);
        }
    }

    static char[] password = "abcdefgh".toCharArray();

    static void display() {
        System.out.println(password);
    }

    public static void main(String[] args) {
        List<String[]> input = FileIO.getFileLinesSplit("advent15.txt", " ");

        for (String[] each : input) {
            Command command;
            int x = 0;
            int y = -1;
            if (each[0].equals("rotate")) {
                command = Command.valueOf(each[0] + "_" + each[1]);
                if (command == Command.rotate_based) {
                    x = (int) each[6].charAt(0);
                } else {
                    x = Integer.parseInt(each[2]);
                }
                y = -1;
            } else {
                command = Command.valueOf(each[0]);
                switch (each[1]) {
                    case "position" :
                        x = Integer.parseInt(each[2]);
                        y = Integer.parseInt(each[5]);
                        break;
                    case "letter" :
                        x = (int) each[2].charAt(0);
                        y = (int) each[5].charAt(0);
                        break;
                    case "positions" :
                        x = Integer.parseInt(each[2]);
                        y = Integer.parseInt(each[4]);
                }
            }
            command.func.accept(x, y);
        }
        display();

        System.out.println("part 2");

        password = "fbgdceah".toCharArray();


        Collections.reverse(input);
        for (String[] each : input) {
            Command command = null;
            int x = 0;
            int y = -1;
            if (each[0].equals("rotate")) {
                switch (each[1]) {
                    case "based" :
                        command = Command.rotate_left;
                        x = reverseLookup[findIndex(each[6].charAt(0))];
                        break;
                    case "left" :
                        command = Command.rotate_right;
                        x = Integer.parseInt(each[2]);
                        break;
                    case "right" :
                        command = Command.rotate_left;
                        x = Integer.parseInt(each[2]);
                }
                y = -1;
            } else {
                command = Command.valueOf(each[0]);
                switch (each[1]) {
                    case "position" :
                        x = Integer.parseInt(each[5]);
                        y = Integer.parseInt(each[2]);
                        break;
                    case "letter" :
                        x = (int) each[5].charAt(0);
                        y = (int) each[2].charAt(0);
                        break;
                    case "positions" :
                        x = Integer.parseInt(each[2]);
                        y = Integer.parseInt(each[4]);
                }
            }
            command.func.accept(x, y);
        }
        display();
    }
}