import java.util.Stack;
/**
* https://leetcode.com/articles/implement-queue-using-stacks/
*/
public class MyQueue {
private Stack mStack = new Stack();
private Stack mStackTmp = new Stack();
// Push element x to the back of queue.
public void push(int x) {
mStack.push(x);
}
// Removes the element from in front of queue.
public void pop() {
dump(mStack, mStackTmp);
mStackTmp.pop();
dump(mStackTmp, mStack);
}
// Get the front element.
public int peek() {
dump(mStack, mStackTmp);
int peek = mStackTmp.peek();
dump(mStackTmp, mStack);
return peek;
}
// Return whether the queue is empty.
public boolean empty() {
return mStack.isEmpty();
}
private void dump(Stack left, Stack right) {
while (!left.isEmpty()) {
right.push(left.pop());
}
}
}