leetcode--Min Stack

Design a stack that supports push, pop, top, and retrieving the minimum element in constant time.

• push(x) -- Push element x onto stack.
• pop() -- Removes the element on top of the stack.
• top() -- Get the top element.
• getMin() -- Retrieve the minimum element in the stack.

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1. class MinStack {  
2.     Stack<Integer> stack1 = new Stack<Integer>();  
3.     Stack<Integer> stack2 = new Stack<Integer>();  
4.       
5.     public void push(int x) {     
6.         if(stack2.size()==0||x<stack2.peek()){  
7.             stack2.add(x);  
8.         }else{  
9.             stack2.add(stack2.peek());  
10.         }  
11.         stack1.add(x);  
12.     }  
13.   
14.     public void pop() {  
15.         stack2.pop();  
16.         stack1.pop();  
17.     }  
18.   
19.     public int top() {    
20.         return stack1.peek();  
21.     }  
22.   
23.     public int getMin() {  
24.         return stack2.peek();  
25.     }  
26. }  

原文链接http://blog.youkuaiyun.com/crazy__chen/article/details/46383623