codewars069 飢餓遊戲：動物園的災難！

Instructions 說明

題目的連接

Story.

A freak power outage at the zoo has caused all of the electric cage doors to malfunction and swing open... All the animals are out and some of them are eating each other! It's a Zoo Disaster! Here is a list of zoo animals, and what they can eat

• antelope eats grass
• big-fish eats little-fish
• bug eats leaves
• bear eats big-fish
• bear eats bug
• bear eats chicken
• bear eats cow
• bear eats leaves
• bear eats sheep
• chicken eats bug
• cow eats grass
• fox eats chicken
• fox eats sheep
• giraffe eats leaves
• lion eats antelope
• lion eats cow
• panda eats leaves
• sheep eats grass

Sample Tests 測試樣例:

import org.junit.Test;
import static org.junit.Assert.assertArrayEquals;

public class ExampleTest {

  @Test
  public void example() {    
    final String input = "fox,bug,chicken,grass,sheep";
    final String[] expected = 	{
      "fox,bug,chicken,grass,sheep", 
      "chicken eats bug", 
      "fox eats chicken", 
      "sheep eats grass", 
      "fox eats sheep", 
      "fox"};
    assertArrayEquals(expected, Dinglemouse.whoEatsWho(input));
  }

@Test
  public void example2() {    
    final String input = "bear,banana,banana,grass,busker,panda,antelope,giraffe,cow,big-fish,banana,sheep,grass,lion";
    final String[] expected = 	{
      "bear,banana,banana,grass,busker,panda,antelope,giraffe,cow,big-fish,banana,sheep,grass,lion", 
      "sheep eats grass", 
      "bear,banana,banana,grass,busker,panda,antelope,giraffe,cow,big-fish,banana,sheep,lion"};
    assertArrayEquals(expected, Dinglemouse.whoEatsWho(input));
  }

}

Solution 解決方案：

//https://www.codewars.com/kata/5902bc7aba39542b4a00003d/train/java
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

public class Dinglemouse {
	private static Map<String, String> map = new HashMap<String, String>();
	static {
		map.put("antelope", "grass");
		map.put("big-fish", "little-fish");
		map.put("bug", "leaves");
		map.put("bear", "big-fish,bug,chicken,cow,leaves,sheep");
		map.put("chicken", "bug");
		map.put("cow", "grass");
		map.put("fox", "chicken,sheep");
		map.put("giraffe", "leaves");
		map.put("lion", "antelope,cow");
		map.put("panda", "leaves");
		map.put("sheep", "grass");

	}

	private static String canEatLeftOrRight(String subject, String left,
			String right) {
		String result = canEat(subject, left);
		if (result.equals("")) {
			return canEat(subject, right);
		}
		return result;

	}

	private static String canEat(String subject, String object) {

		if (!map.containsKey(subject) || "".equals(object)) {
			return "";
		}
		if (map.get(subject).indexOf(object) != -1) {
			return String.format("%s eats %s", subject, object);
		}
		return "";
	}

	private static StringBuffer reduce(String[] arr, int subject, String left,
			String right, String rule) {
		String target = rule.split(" ")[2];
		int purge = -1;
		if (target.equals(left)) {
			purge = subject - 1;
		}
		if (target.equals(right)) {
			purge = subject + 1;
		}
		StringBuffer sb = new StringBuffer();
		for (int i = 0; i < arr.length; i++) {
			if (i != purge) {
				sb.append(arr[i]).append(",");
			}
		}
		int len = sb.length();
		if (sb.charAt(len - 1) == ',') {
			sb.deleteCharAt(len - 1);
		}
		return sb;
	}

	public static String[] whoEatsWho(final String zoo) {
		List<String> list = new ArrayList<String>();
		list.add(zoo);
		StringBuffer sb = new StringBuffer(zoo);
		boolean reduceable = true;
		Label: while (reduceable) {
			String[] arr = sb.toString().split(",");
			if (arr.length < 2) {
				break;
			}
			for (int i = 0; i < arr.length; i++) {
				String subject = arr[i];
				String left = i > 0 ? arr[i - 1] : "";
				String right = i < arr.length - 1 ? arr[i + 1] : "";

				String check = canEatLeftOrRight(subject, left, right);

				if (!check.equals("")) {
					list.add(check);
					sb = reduce(arr, i, left, right, check);
					break;
				}
				if (i == arr.length - 1) {
					reduceable = false;
					break Label;
				}
			}

		}
		list.add(sb.toString());
		return list.toArray(new String[0]);
		// return new String[]{zoo, zoo};
	}

}