Create 0225-implement-stack-using-queues.java

The solution that is provided in the video https://www.youtube.com/watch?v=rW4vm0-DLYc uses a stack operation to implement the top() method. My java translation has been modified to only use queue operations, using the same algorithm as the pop() method uses.

Author: AP-Repositories

Diff for: java/0225-implement-stack-using-queues.java

@@ -0,0 +1,31 @@
+class MyStack {
+    Deque<Integer> q;
+    public MyStack() {
+       this.q = new ArrayDeque<>(); 
+    }
+    
+    public void push(int x) {
+        this.q.addLast(x);
+    }
+    
+    public int pop() {
+        int size = this.q.size();
+        for(int i = 0; i < size - 1; i++)
+            this.push(this.q.pollFirst());
+        return this.q.pollFirst();
+    }
+    
+    public int top() {
+        int size = q.size();
+        for(int i = 0; i < size - 1; i++)
+            this.push(this.q.pollFirst());
+        
+        int res = this.q.peekFirst();
+        this.push(this.q.pollFirst());
+        return res;
+    }
+    
+    public boolean empty() {
+        return this.q.size() == 0;
+    }
+}