Updated exercise 1.3.9

src/chapter1/section3/Exercise9.java

@@ -6,10 +6,11 @@
 /**
  * Created by Rene Argento
  */
+// Thanks to ru2saig (https://github.com/ru2saig) for reporting that the sqrt unary operator should be included.
+// https://github.com/reneargento/algorithms-sedgewick-wayne/issues/308
 public class Exercise9 {
 
     private static String getInfixExpression(String input) {
-
         Stack<String> operands = new Stack<>();
         Stack<String> operators = new Stack<>();
 
@@ -21,14 +22,20 @@ private static String getInfixExpression(String input) {
             } else if (value.equals("+")
                     || value.equals("-")
                     || value.equals("*")
-                    || value.equals("/")) {
+                    || value.equals("/")
+                    || value.equals("sqrt")) {
                 operators.push(value);
             } else if (value.equals(")")) {
+                String subExpression;
                 String operator = operators.pop();
                 String value2 = operands.pop();
-                String value1 = operands.pop();
 
-                String subExpression = "( " + value1 + " " + operator + " " + value2 + " )";
+                if (operator.equals("sqrt")) {
+                    subExpression = operator + " ( " + value2 + " )";
+                } else {
+                    String value1 = operands.pop();
+                    subExpression = "( " + value1 + " " + operator + " " + value2 + " )";
+                }
                 operands.push(subExpression);
             } else {
                 operands.push(value);
@@ -37,8 +44,10 @@ private static String getInfixExpression(String input) {
         return operands.pop();
     }
 
-    // Parameter example: "1 + 2 ) * 3 - 4 ) * 5 - 6 ) ) )"
-    public static void main(String args[]) {
+    // Parameter examples:
+    // "1 + 2 ) * 3 - 4 ) * 5 - 6 ) ) )"
+    // "2 + 3 ) * 5 + sqrt 7.0 ) ) )"
+    public static void main(String[] args) {
         String input = args[0];
         StdOut.println(getInfixExpression(input));
     }