refactor 150

Author: fishercoder1534

src/main/java/com/fishercoder/solutions/_150.java

@@ -5,61 +5,88 @@
 import java.util.Stack;
 
 /**
- *  Evaluate the value of an arithmetic expression in Reverse Polish Notation.
-
- Valid operators are +, -, *, /. Each operand may be an integer or another expression.
-
- Some examples:
-
- ["2", "1", "+", "3", "*"] -> ((2 + 1) * 3) -> 9
- ["4", "13", "5", "/", "+"] -> (4 + (13 / 5)) -> 6
-
+ * 150. Evaluate Reverse Polish Notation
+ *
+ * Evaluate the value of an arithmetic expression in Reverse Polish Notation.
+ *
+ * Valid operators are +, -, *, /. Each operand may be an integer or another expression.
+ *
+ * Note:
+ *
+ *     Division between two integers should truncate toward zero.
+ *     The given RPN expression is always valid. That means the expression would always evaluate to a result and there won't be any divide by zero operation.
+ *
+ * Example 1:
+ *
+ * Input: ["2", "1", "+", "3", "*"]
+ * Output: 9
+ * Explanation: ((2 + 1) * 3) = 9
+ *
+ * Example 2:
+ *
+ * Input: ["4", "13", "5", "/", "+"]
+ * Output: 6
+ * Explanation: (4 + (13 / 5)) = 6
+ *
+ * Example 3:
+ *
+ * Input: ["10", "6", "9", "3", "+", "-11", "*", "/", "*", "17", "+", "5", "+"]
+ * Output: 22
+ * Explanation:
+ *   ((10 * (6 / ((9 + 3) * -11))) + 17) + 5
+ * = ((10 * (6 / (12 * -11))) + 17) + 5
+ * = ((10 * (6 / -132)) + 17) + 5
+ * = ((10 * 0) + 17) + 5
+ * = (0 + 17) + 5
+ * = 17 + 5
+ * = 22
  */
 public class _150 {
 
-    public int evalRPN(String[] tokens) {
-        Stack<String> stack = new Stack<String>();
-        Set<String> op = new HashSet();
-        op.add("+");
-        op.add("-");
-        op.add("*");
-        op.add("/");
+    public static class Solution1 {
+        public int evalRPN(String[] tokens) {
+            Stack<String> stack = new Stack<>();
+            Set<String> op = new HashSet();
+            op.add("+");
+            op.add("-");
+            op.add("*");
+            op.add("/");
 
-        int exp = 0;
-        String operand1 = "";
-        String operand2 = "";
-        for (int i = 0; i < tokens.length;) {
-            while ((i < tokens.length) && (!op.contains(tokens[i]))) {
-                stack.push(tokens[i]);
-                i++;
-            }
-            if (i == tokens.length) {
-                if (!stack.isEmpty()) {
-                    return Integer.parseInt(stack.pop());
-                }
-            } else if (op.contains(tokens[i])) {
-                if (!stack.isEmpty()) {
-                    operand2 = stack.pop();
+            int exp = 0;
+            String operand1 = "";
+            String operand2 = "";
+            for (int i = 0; i < tokens.length; ) {
+                while ((i < tokens.length) && (!op.contains(tokens[i]))) {
+                    stack.push(tokens[i]);
+                    i++;
                 }
-                if (!stack.isEmpty() && !op.contains(stack.peek())) {
-                    operand1 = stack.pop();
+                if (i == tokens.length) {
+                    if (!stack.isEmpty()) {
+                        return Integer.parseInt(stack.pop());
+                    }
+                } else if (op.contains(tokens[i])) {
+                    if (!stack.isEmpty()) {
+                        operand2 = stack.pop();
+                    }
+                    if (!stack.isEmpty() && !op.contains(stack.peek())) {
+                        operand1 = stack.pop();
+                    }
+                    if (tokens[i].equals("+")) {
+                        exp = Integer.parseInt(operand1) + Integer.parseInt(operand2);
+                    } else if (tokens[i].equals("-")) {
+                        exp = Integer.parseInt(operand1) - Integer.parseInt(operand2);
+                    } else if (tokens[i].equals("*")) {
+                        exp = Integer.parseInt(operand1) * Integer.parseInt(operand2);
+                    } else if (tokens[i].equals("/")) {
+                        exp = Integer.parseInt(operand1) / Integer.parseInt(operand2);
+                    } else {
+                        exp = Integer.parseInt(operand2);
+                    }
+                    stack.push(String.valueOf(exp));
+                    i++;
                 }
-                if (tokens[i].equals("+")) {
-                    exp = Integer.parseInt(operand1) + Integer.parseInt(operand2);
-                } else if (tokens[i].equals("-")) {
-                    exp = Integer.parseInt(operand1) - Integer.parseInt(operand2);
-                } else if (tokens[i].equals("*")) {
-                    exp = Integer.parseInt(operand1) * Integer.parseInt(operand2);
-                } else if (tokens[i].equals("/")) {
-                    exp = Integer.parseInt(operand1) / Integer.parseInt(operand2);
-                } else {
-                    exp = Integer.parseInt(operand2);
-                }
-                stack.push(String.valueOf(exp));
-                i++;
             }
+            return Integer.parseInt(stack.pop());
         }
-        return Integer.parseInt(stack.pop());
     }
-
 }