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MyStack.java
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63 lines (52 loc) · 1.63 KB
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class MyStack {
private Queue<Integer> queue1 = new LinkedList<Integer>();
private Queue<Integer> queue2 = new LinkedList<Integer>();
// Push element x onto stack.
public void push(int x) {
Queue<Integer> notEmptyQueue = null;
if (queue1.isEmpty()) {
notEmptyQueue = queue2;
} else {
notEmptyQueue = queue1;
}
notEmptyQueue.offer(x);
}
// Removes the element on top of the stack.
public void pop() {
Queue<Integer> emptyQueue = null;
Queue<Integer> notEmptyQueue = null;
if (queue1.isEmpty()) {
emptyQueue = queue1;
notEmptyQueue = queue2;
} else {
emptyQueue = queue2;
notEmptyQueue = queue1;
}
while (notEmptyQueue.size() > 1) {
emptyQueue.offer(notEmptyQueue.poll());
}
notEmptyQueue.poll();
}
// Get the top element.
public int top() {
Queue<Integer> emptyQueue = null;
Queue<Integer> notEmptyQueue = null;
if (queue1.isEmpty()) {
emptyQueue = queue1;
notEmptyQueue = queue2;
} else {
emptyQueue = queue2;
notEmptyQueue = queue1;
}
while (notEmptyQueue.size() > 1) {
emptyQueue.offer(notEmptyQueue.poll());
}
int result = notEmptyQueue.poll();
emptyQueue.offer(result);
return result;
}
// Return whether the stack is empty.
public boolean empty() {
return queue1.isEmpty() && queue2.isEmpty();
}
}