Google Code Jam Winning solution Round 3 - Magical, Marvelous Tour

Main.java

import java.io.BufferedWriter;
import java.util.InputMismatchException;
import java.util.NoSuchElementException;
import java.math.BigInteger;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.io.Writer;
import java.io.IOException;
import java.io.FileInputStream;
import java.util.Arrays;
import java.io.InputStream;
import java.io.FilenameFilter;
import java.util.Locale;
import java.io.OutputStreamWriter;
import java.util.Comparator;
import java.io.FileOutputStream;
import java.io.File;

/**
 * Built using CHelper plug-in
 * Actual solution is at the top
 * @author Egor Kulikov (egor@egork.net)
 */
public class Main {
	public static void main(String[] args) {
		Locale.setDefault(Locale.US);
		InputStream inputStream;
		try {
			final String regex = "B-(small|large).*[.]in";
			File directory = new File(".");
			File[] candidates = directory.listFiles(new FilenameFilter() {
				public boolean accept(File dir, String name) {
					return name.matches(regex);
				}
			});
			File toRun = null;
			for (File candidate : candidates) {
				if (toRun == null || candidate.lastModified() > toRun.lastModified())
					toRun = candidate;
			}
			inputStream = new FileInputStream(toRun);
		} catch (IOException e) {
			throw new RuntimeException(e);
		}
		OutputStream outputStream;
		try {
			outputStream = new FileOutputStream("b.out");
		} catch (IOException e) {
			throw new RuntimeException(e);
		}
		InputReader in = new InputReader(inputStream);
		OutputWriter out = new OutputWriter(outputStream);
		TaskB solver = new TaskB();
		int testCount = Integer.parseInt(in.next());
		for (int i = 1; i <= testCount; i++)
			solver.solve(i, in, out);
		out.close();
	}
}

class TaskB {
    public void solve(int testNumber, InputReader in, OutputWriter out) {
		int dianaHit = in.readInt();
		int towerHit = in.readInt();
		int count = in.readInt();
		int[] health = new int[count];
		int[] gold = new int[count];
		IOUtils.readIntArrays(in, health, gold);
		int[][] answer = new int[count + 1][2000];
		ArrayUtils.fill(answer, Integer.MIN_VALUE);
		answer[0][1] = 0;
		for (int i = 0; i < count; i++) {
			int towerKill = (health[i] + towerHit - 1) / towerHit;
			for (int j = 0; j < 2000; j++) {
				if (answer[i][j] == Integer.MIN_VALUE)
					continue;
				for (int k = 0; k < towerKill; k++) {
					int remaining = health[i] - k * towerHit;
					int dianaKill = (remaining + dianaHit - 1) / dianaHit;
					if (dianaKill <= k + j)
						answer[i + 1][k + j - dianaKill] = Math.max(answer[i + 1][k + j - dianaKill], answer[i][j] + gold[i]);
				}
				answer[i + 1][j + towerKill] = Math.max(answer[i + 1][j + towerKill], answer[i][j]);
			}
		}
		out.printLine("Case #" + testNumber + ":", ArrayUtils.maxElement(answer[count]));
    }
}

class InputReader {

	private InputStream stream;
	private byte[] buf = new byte[1024];
	private int curChar;
	private int numChars;
	private SpaceCharFilter filter;

	public InputReader(InputStream stream) {
		this.stream = stream;
	}

	public int read() {
		if (numChars == -1)
			throw new InputMismatchException();
		if (curChar >= numChars) {
			curChar = 0;
			try {
				numChars = stream.read(buf);
			} catch (IOException e) {
				throw new InputMismatchException();
			}
			if (numChars <= 0)
				return -1;
		}
		return buf[curChar++];
	}

	public int readInt() {
		int c = read();
		while (isSpaceChar(c))
			c = read();
		int sgn = 1;
		if (c == '-') {
			sgn = -1;
			c = read();
		}
		int res = 0;
		do {
			if (c < '0' || c > '9')
				throw new InputMismatchException();
			res *= 10;
			res += c - '0';
			c = read();
		} while (!isSpaceChar(c));
		return res * sgn;
	}

	public String readString() {
		int c = read();
		while (isSpaceChar(c))
			c = read();
		StringBuilder res = new StringBuilder();
		do {
			if (Character.isValidCodePoint(c))
				res.appendCodePoint(c);
			c = read();
		} while (!isSpaceChar(c));
		return res.toString();
	}

	public boolean isSpaceChar(int c) {
		if (filter != null)
			return filter.isSpaceChar(c);
		return isWhitespace(c);
	}

	public static boolean isWhitespace(int c) {
		return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
	}

	public String next() {
		return readString();
	}

	public interface SpaceCharFilter {
		public boolean isSpaceChar(int ch);
	}
}

class OutputWriter {
	private final PrintWriter writer;

	public OutputWriter(OutputStream outputStream) {
		writer = new PrintWriter(new BufferedWriter(new OutputStreamWriter(outputStream)));
	}

	public OutputWriter(Writer writer) {
		this.writer = new PrintWriter(writer);
	}

	public void print(Object...objects) {
		for (int i = 0; i < objects.length; i++) {
			if (i != 0)
				writer.print(' ');
			writer.print(objects[i]);
		}
	}

	public void printLine(Object...objects) {
		print(objects);
		writer.println();
	}

	public void close() {
		writer.close();
	}

}

class IOUtils {

	public static void readIntArrays(InputReader in, int[]... arrays) {
		for (int i = 0; i < arrays[0].length; i++) {
			for (int j = 0; j < arrays.length; j++)
				arrays[j][i] = in.readInt();
		}
	}

}

class ArrayUtils {

	public static void fill(int[][] array, int value) {
		for (int[] row : array)
			Arrays.fill(row, value);
	}

	public static int maxElement(int[] array) {
		return maxElement(array, 0, array.length);
	}

	public static int maxElement(int[] array, int from, int to) {
		int result = Integer.MIN_VALUE;
		for (int i = from; i < to; i++)
			result = Math.max(result, array[i]);
		return result;
	}

}