关于leetcode个人解题总结:刷题2用队列实现栈

Leetcode：用队列实现栈
要害：元素入队后，把元素 x 前的其余元素从新出队，再入队，这样 x 就在队头了，其余元素采纳同样办法入队。

class MyStack {
    Queue<Integer> queue;
    /** Initialize your data structure here. */
    public MyStack() {queue = new LinkedList<Integer>();
    }
    
    /** Push element x onto stack. */
    public void push(int x) {
        // 获取入队前的元素个数
        int length = queue.size();
        queue.offer(x);
        // 将 x 前的元素从新入队再出队，最终 x 排在队头
        for (int i = 0;i < length;i++){queue.offer(queue.poll());
        }
        
    }
   
    /** Removes the element on top of the stack and returns that element. */
    public int pop() {if(empty()){return -1;}else{return queue.poll();
        }
    }

    
    /** Get the top element. */
    public int top() {if(empty()){return -1;}else{return queue.peek();
        }
    }
    
    /** Returns whether the stack is empty. */
    public boolean empty() {if(queue.isEmpty()){return true;}else{return false;}
    }
}