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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. 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). Update (2015-06-11): The class name of the Java function had been updated to MyStack instead of Stack.
class MyStack { List<Integer> list=new ArrayList<Integer>(); // Push element x onto stack. public void push(int x) { list.add(x); } // Removes the element on top of the stack. public void pop() { int len=list.size(); if(len>0){ list.remove(len-1); } } // Get the top element. public int top() { int len=list.size(); if(len>0){ return list.get(len-1); } else{ return 0; } } // Return whether the stack is empty. public boolean empty() { int len=list.size(); if(len==0){ return true; } else{ return false; } } }
LeetCode-Implement Stack using Queues
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原文地址：http://www.cnblogs.com/incrediblechangshuo/p/5513948.html
