EASY/src/easy/ImplementQueueUsingStacks.java

fishercoder1534 · fishercoder1534 · commit e78bcb8a786a · 2016-09-28T12:31:18.000-07:00
diff --git a/EASY/src/easy/ImplementQueueUsingStacks.java b/EASY/src/easy/ImplementQueueUsingStacks.java
@@ -0,0 +1,38 @@
+package easy;
+
+import java.util.Stack;
+
+public class ImplementQueueUsingStacks {
+
+    class MyQueue {
+        
+        Stack<Integer> input = new Stack();
+        Stack<Integer> output = new Stack();
+        
+        // Push element x to the back of queue.
+        public void push(int x) {
+            input.push(x);
+        }
+
+        // Removes the element from in front of queue.
+        public void pop() {
+            peek();
+            output.pop();
+        }
+
+        // Get the front element.
+        public int peek() {
+            if(output.isEmpty()){
+                while(!input.isEmpty()){
+                    output.push(input.pop());
+                }
+            }
+            return output.peek();
+        }
+
+        // Return whether the queue is empty.
+        public boolean empty() {
+            return input.isEmpty() && output.isEmpty();
+        }
+    }
+}
