Create Implement Stack using Queues.java

Author: abhijit-003

Java/Implement Stack using Queues.java

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+//225 Implement Stack using Queues
+public class MyStack {
+    //1st approach using only one queue
+    // private Queue<Integer> q;
+
+    // public MyStack() {
+    //     q = new LinkedList<>();
+    // }
+
+    // public void push(int x) {
+    //     q.add(x);
+    //     for (int i = 1; i < q.size(); i++) {
+    //         q.add(q.remove());
+    //     }
+    // }
+
+    // public int pop() {
+    //     return q.remove();
+    // }
+
+    // public int top() {
+    //     return q.peek();
+    // }
+
+    // public boolean empty() {
+    //     return q.isEmpty();
+    // }
+
+    //2nd approach 
+    //using 2 queue
+    private Queue<Integer> q1;
+    private Queue<Integer> q2;
+    public MyStack(){
+        q1 = new LinkedList<>();
+        q2 = new LinkedList<>();
+    }
+    public void push(int x){
+        q2.add(x);
+        while(!q1.isEmpty()){
+            q2.add(q1.remove());
+        }
+        while(!q2.isEmpty()){
+            q1.add(q2.remove());
+        }
+    }
+    public int pop(){
+        if(!q1.isEmpty())
+        return q1.remove();
+        return -1;
+    }
+    public int top(){
+        if(!q1.isEmpty())
+        return q1.peek();
+        return -1;
+    }
+    public boolean empty(){
+        return q1.isEmpty();
+    }
+}
+
+/**
+ * Your MyStack object will be instantiated and called as such:
+ * MyStack obj = new MyStack();
+ * obj.push(x);
+ * int param_2 = obj.pop();
+ * int param_3 = obj.top();
+ * boolean param_4 = obj.empty();
+ */