[2015-12-30] Challenge #247 [Intermediate] Moving (diagonally) Up in Life

DelannoyMain.java

package com.sandbox;

import java.io.File;
import java.io.IOException;
import java.nio.file.Files;
import java.util.List;
import java.util.Set;
import java.util.TreeSet;

public class DelannoyMain {
	public static class Pair implements Comparable<Pair> {
		public int x;
		public int y;

		public Pair(int x, int y) {
			this.x = x;
			this.y = y;
		}

		@Override
		public int compareTo(Pair o) {
			int xDiff = x - o.x;
			if (xDiff == 0) {
				return y - o.y;
			} else {
				return xDiff;
			}
		}

	}

	public static void main(String... args) throws IOException {
		File file = new File("/temp/delannoy.txt");
		List<String> lines = Files.readAllLines(file.toPath());
		String[] firstLine = lines.remove(0).split(",[\\s]*");
		int width = Integer.parseInt(firstLine[0]);
		int height = Integer.parseInt(firstLine[1]);
		Set<Pair> pairs = new TreeSet<>();
		for (int i = 0; i < height; i++) {
			String line = lines.remove(0);
			String[] split = line.split("");
			for (int j = 0; j < width; j++) {
				if ("X".equals(split[j])) {
					pairs.add(new Pair(j, (height - 1) - i));
				}
			}
		}
		long totalPermutations = countPermutations(pairs);
		if (totalPermutations == -1) {
			System.out.println("<invalid input>");
		} else {
			System.out.println(totalPermutations);
		}
	}

	public static long countPermutations(Set<Pair> pairs) {
		Pair[] iHateJavaSets = pairs.toArray(new Pair[0]);
		long total = 1;
		for (int i = 0; i < pairs.size() - 1; i++) {
			Pair firstPair = iHateJavaSets[i];
			Pair secondPair = iHateJavaSets[i + 1];
			if ((secondPair.x - firstPair.x) < 0 || (secondPair.y - firstPair.y) < 0) {
				return -1;
			}
			total *= recursiveDelannoy(secondPair.x - firstPair.x, secondPair.y - firstPair.y);
		}
		return total;
	}

	public static int recursiveDelannoy(int x, int y) {
		if (x == 0 || y == 0) {
			return 1;
		} else {
			return recursiveDelannoy(x - 1, y) + recursiveDelannoy(x, y - 1) + recursiveDelannoy(x - 1, y - 1);
		}
	}
}