Added comments

Author: rampatra

src/main/java/com/ctci/stacksandqueues/QueueViaStacks.java

@@ -4,6 +4,8 @@
 import java.util.Stack;
 
 /**
+ * Implement a queue using two stacks. No other data structures to be used.
+ *
  * @author rampatra
  * @since 2019-02-06
  */

src/main/java/com/ctci/stacksandqueues/SortStack.java

@@ -4,6 +4,10 @@
 import java.util.Stack;
 
 /**
+ * Write a program to sort a stack such that the smallest items are on the top. You can use an additional temporary
+ * stack, but you may not copy the elements into any other data structure (such as an array). The stack supports the
+ * following operations: push, pop, peek, and isEmpty.
+ * 
  * @author rampatra
  * @since 2019-02-08
  */

src/main/java/com/ctci/stacksandqueues/StackOfPlates.java

@@ -7,6 +7,12 @@
 import java.util.Stack;
 
 /**
+ * Imagine a (literal) stack of plates. If the stack gets too high, it might topple. Therefore, in real life, we
+ * would likely start a new stack when the previous stack exceeds some threshold. Implement a data structure
+ * SetOfStacks that mimics this. SetOfStacks should be composed of several stacks and should create a new stack once
+ * the previous one exceeds capacity. SetOfStacks.push() and SetOfStacks. pop() should behave identically to a single
+ * stack (that is, pop() should return the same values as it would if there were just a single stack).
+ *
  * @author rampatra
  * @since 2019-02-08
  */