Problem 05 - Ch 03

README.md

@@ -27,7 +27,7 @@ Java Solutions for Cracking the Coding Interview - 6th Edition
 - [X] [02 - Stack Min](../master/src/com/deepak/ctci/Ch03_Stacks_And_Queues/Problem_02.java)
 - [X] [03 - Stack of Plates](../master/src/com/deepak/ctci/Ch03_Stacks_And_Queues/Problem_03.java)
 - [X] [04 - Queue via Stacks](../master/src/com/deepak/ctci/Ch03_Stacks_And_Queues/Problem_04.java)
-- [ ] 05 - Sort Stack
+- [X] [05 - Sort Stack](../master/src/com/deepak/ctci/Ch03_Stacks_And_Queues/Problem_05.java)
 - [ ] 06 - Animal Shelter
 
 **Ch 04 - Trees and Graphs**

src/com/deepak/ctci/Ch03_Stacks_And_Queues/Problem_05.java

@@ -4,6 +4,8 @@
  */
 package com.deepak.ctci.Ch03_Stacks_And_Queues;
 
+import java.util.Stack;
+
 /**
  * <br> Problem Statement :
  * 
@@ -19,4 +21,32 @@
  */
 public class Problem_05 {
 
+	/**
+	 * Method to sort stack
+	 * 
+	 * @param input
+	 * @return {@link Stack}
+	 */
+	public static Stack<Integer> sortStack(Stack<Integer> input) {
+		/* If input is null, no processing needed */
+		if (input == null) {
+			return null;
+		}
+		/*Create a temp stack */
+		Stack<Integer> tempStack = new Stack<>();
+		/* Keep going until input is not empty */
+		while (!input.isEmpty()) {
+			/* Pop value from input */
+			int tempValue = input.pop();
+			/* We want smallest one at the bottom. So keep comparing and 
+			 * if temp stack has bigger item, pop it and push it to input stack */
+			while (!tempStack.isEmpty() && tempStack.peek() > tempValue) {
+				input.push(tempStack.pop());
+			}
+			/* Push temp value to the temp stack */
+			tempStack.push(tempValue);
+		}
+		return tempStack;
+	}
+
 }

test/com/deepak/ctci/Ch03_Stacks_And_Queues/Problem_05_Test.java

@@ -0,0 +1,44 @@
+/**
+ * Cracking-The-Coding-Interview
+ * Problem_04_Test.java
+ */
+package com.deepak.ctci.Ch03_Stacks_And_Queues;
+
+import java.util.Stack;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+/**
+ * Test cases for Problem 05
+ * 
+ * @author Deepak
+ */
+public class Problem_05_Test {
+
+	/**
+	 * Test cases for sorting a stack
+	 */
+	@Test
+	public void testSortStack() {
+		Stack<Integer> input = new Stack<>();
+		input.push(2);
+		input.push(9);
+		input.push(7);
+		input.push(3);
+		input.push(1);
+		input.push(5);
+		input.push(10);
+		Assert.assertTrue(input.size() == 7);
+		Stack<Integer> output = Problem_05.sortStack(input);
+		Assert.assertTrue(output.pop() == 10);
+		Assert.assertTrue(output.pop() == 9);
+		Assert.assertTrue(output.pop() == 7);
+		Assert.assertTrue(output.pop() == 5);
+		Assert.assertTrue(output.pop() == 3);
+		Assert.assertTrue(output.pop() == 2);
+		Assert.assertTrue(output.pop() == 1);
+		Assert.assertTrue(output.size() == 0);
+	}
+
+}