add code of 232

Author: Li Li

Algorithms Basics/Chapter 4. Stack and Queue/232. Implement Queue using Stacks.cs

@@ -0,0 +1,51 @@
+// use two stack.
+public class MyQueue {
+    private Stack<int> s1;
+    private Stack<int> s2;
+    private int front;
+    /** Initialize your data structure here. */
+    public MyQueue() {
+        s1 = new Stack<int>();
+        s2 = new Stack<int>();
+    }
+
+    /** Push element x to the back of queue. */
+    public void Push(int x) {
+        if (s1.Count == 0) {
+            front = x;
+        }
+        s1.Push(x);
+    }
+
+    /** Removes the element from in front of queue and returns that element. */
+    public int Pop() {
+        if (s2.Count == 0) {
+            while (s1.Count > 0) {
+                s2.Push(s1.Pop());
+            }
+        }
+        return s2.Pop();
+    }
+
+    /** Get the front element. */
+    public int Peek() {
+        if (s2.Count == 0) {
+            return front;
+        }
+        return s2.Peek();
+    }
+
+    /** Returns whether the queue is empty. */
+    public bool Empty() {
+        return s1.Count == 0 && s2.Count == 0;
+    }
+}
+
+/**
+    * Your MyQueue object will be instantiated and called as such:
+    * MyQueue obj = new MyQueue();
+    * obj.Push(x);
+    * int param_2 = obj.Pop();
+    * int param_3 = obj.Peek();
+    * bool param_4 = obj.Empty();
+    */