aoc/day03.java

import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;

public class day03 {

	public static void main(String[] args) throws IOException {
		String gammaCalc = "";
		String epsilonCalc = "";
		int gammaVal = 0;
		int epsilonVal = 0;

		int finalAns = 0;

		String line;

		BufferedReader in = new BufferedReader(new FileReader("day03-input.txt"));
		line = in.readLine();

		int numLengthHuman = line.length();

		// [0] will not have anything i think
		int[] zeroCounter = new int[numLengthHuman + 1];
		int[] oneCounter = new int[numLengthHuman + 1];
		// temporary var, concat into an int for gammaVal/ epsilonVal.
		String[] tempC = new String[numLengthHuman + 1];

		while (line != null) {

			for (int i = 1; i <= line.length(); i++) {

				int currentNum = Integer.valueOf(line.substring(i - 1, i));

				if (currentNum == 0) {
					zeroCounter[i]++;
				}
				if (currentNum == 1) {
					oneCounter[i]++;
				}
			}

			line = in.readLine();
		}
		in.close();

		// calc gamma
		for (int i = 1; i <= numLengthHuman; i++) {

			if (zeroCounter[i] > oneCounter[i]) {
				tempC[i] = "0";
			} else {
				tempC[i] = "1";
			}
			
			gammaCalc = gammaCalc + tempC[i];
		}

		gammaVal = Integer.parseInt(gammaCalc, 2); // some weird conversion thing?

		// calc epsilon
		for (int i = 1; i <= numLengthHuman; i++) {

			if (zeroCounter[i] > oneCounter[i]) {
				tempC[i] = "1"; // this time, one is the least
			} else {
				tempC[i] = "0";
			}

			epsilonCalc = epsilonCalc + tempC[i];
		}

		epsilonVal = Integer.parseInt(epsilonCalc, 2);

		finalAns = gammaVal * epsilonVal;
		System.out.println(finalAns);

	}
}