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### by Sumit Chourasia | Oct 03, 2020 | Category :coding | Tags : algorithmdata-structureeasyleetcodestack #### Implement Stack using Queues - Stack - Easy - LeetCode

Implement the following operations of a stack using queues.

push(x) -- Push element x onto stack.
pop() -- Removes the element on top of the stack.
top() -- Get the top element.
empty() -- Return whether the stack is empty.
Example:

MyStack stack = new MyStack();

stack.push(1);
stack.push(2);
stack.top();   // returns 2
stack.pop();   // returns 2
stack.empty(); // returns false
Notes:

You must use only standard operations of a queue -- which means only push to back, peek/pop from front, size, and is empty operations are valid.
Depending on your language, queue may not be supported natively. You may simulate a queue by using a list or deque (double-ended queue), as long as you use only standard operations of a queue.
You may assume that all operations are valid (for example, no pop or top operations will be called on an empty stack).

``````public class MyStack {

Queue<int> queue1;
Queue<int> queue2;
/** Initialize your data structure here. */
public MyStack() {
queue1 = new Queue<int>();
queue2 = new Queue<int>();
}

/** Push element x onto stack. */
public void Push(int x) {
queue2.Enqueue(x);
while(queue1.Count>0){
queue2.Enqueue(queue1.Dequeue());
}
Queue<int> temp = queue1;
queue1 = queue2;
queue2 = temp;
}

/** Removes the element on top of the stack and returns that element. */
public int Pop() {
if(queue1.Count<1){
return -1;
}
return queue1.Dequeue();
}

/** Get the top element. */
public int Top() {
if(queue1.Count<1){
return -1;
}
return queue1.Peek();
}

/** Returns whether the stack is empty. */
public bool Empty() {
return queue1.Count()<1;
}
}

/**
* 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();
* bool param_4 = obj.Empty();
*/``````

Time Complexity: O(n)

Space Complexity: O(n)