SimplifyExpressionTest

import junit.framework.TestCase;
import java.util.Stack;

public class SimplifyExpressionTest extends TestCase {

    private static String simplifyExpression(final String inputExpression) {
        final StringBuilder simplifiedExpression = new StringBuilder();

        // Implementation logic here:
        final Stack<Boolean> signStack = new Stack<>();
        boolean positiveSign = true;
        signStack.push(positiveSign);

        for (final char chr : inputExpression.toCharArray()) {

            // >>>---> Super Secret Implementation Logic Here. <---<<< //

        }

        return simplifiedExpression.toString();
    }

    public void test1() {
        assertSimpifiedExpressionEquals("-a-b-c", "-(a+b+c)");
    }

    public void test2() {
        assertSimpifiedExpressionEquals("a-b-c+d", "a-b-(c-d)");
    }

    public void test3() {
        assertSimpifiedExpressionEquals("a-b+c+d-e", "a-(b-(c+d)+e)");
    }

    public void test4() {
        assertSimpifiedExpressionEquals("a-b+c+d-e+f-g", "a-(b-(c+d)+(e-f)+g)");
    }

    public void tests() {
        assertSimpifiedExpressionEquals("a", "a");
        assertSimpifiedExpressionEquals("a", "+a");
        assertSimpifiedExpressionEquals("-a", "-a");
        assertSimpifiedExpressionEquals("a+b", "a+b");
        assertSimpifiedExpressionEquals("a-b", "a-b");

        assertSimpifiedExpressionEquals("-a-b", "-(a+b)");
        assertSimpifiedExpressionEquals("-a+b", "-(a-b)");

        assertSimpifiedExpressionEquals("-a", "-(a)");
        assertSimpifiedExpressionEquals("a", "-(-(a))");
        assertSimpifiedExpressionEquals("-a", "-(-(-(a)))");

        assertSimpifiedExpressionEquals("-a+b-c+d-e", "-(a-(b-(c-(d-e))))");
        assertSimpifiedExpressionEquals("-a+b-c+d", "-(a-(b)+(c-d))");
    }

    private static void assertSimpifiedExpressionEquals(final String expectedSimpifiedExpression, final String inputExpression) {
        assertEquals("For expression <" + inputExpression + ">;", expectedSimpifiedExpression, simplifyExpression(inputExpression));
    }

}