Solution5.java

public class Solution5 {

	static int getValue(final int lastFunctionOperator, final String term) {
		switch (lastFunctionOperator) {
			case 0:
				return Integer.parseInt(term);
			case 1:
				return Integer.parseInt(term);
			case 2:
				return -1 * Integer.parseInt(term);
		}
		return 0; // never reached
	}

	public static void main(String[] args) {
		int max = (int) Math.pow(3, 8);

		for (int n = 0; n < max; ++n) {
			int sum = 0;
			String sentence = "";
			String term = "";

			int lastFunctionOperator = 0;

			for (int i = 1; i <=9 ; ++i) {
				term += i;

				// 0 = nothing
				// 1 = plus
				// 2 = subtract
				int operator = (n / ((int) Math.pow(3, i - 1))) % 3;

				switch (operator) {
					case 0:
						break;
					default:
						sum += getValue(lastFunctionOperator, term);
						switch (lastFunctionOperator) {
							case 0: break;
							case 1: sentence += " + "; break;
							case 2: sentence += " - "; break;
						}
						sentence += term;
						term = "";
						lastFunctionOperator = operator;
						break;
				}

			} // for i

			sum += getValue(lastFunctionOperator, term);
			switch (lastFunctionOperator) {
				case 0: break;
				case 1: sentence += " + "; break;
				case 2: sentence += " - "; break;
			}
			sentence += term;

			if (sum == 100) {
				System.out.println(sentence + " = 100");
			}

		} // for n
	}
}