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.

Solution:

 1 class MinStack {
 2     Stack<Integer> stack;
 3     int curMin;
 4     Stack<Integer> minStack;
 5 
 6 
 7     public MinStack(){
 8         stack = new Stack<Integer>();
 9         curMin = Integer.MAX_VALUE;
10         minStack = new Stack<Integer>();
11     }
12 
13 
14     public void push(int x) {
15         stack.push(x);
16         if (x<=curMin){
17             minStack.push(x);
18             curMin = x;
19         }
20     }
21 
22     public void pop() {
23         int val = stack.peek();
24         stack.pop();
25         if (val==curMin){
26             minStack.pop();
27             if (!minStack.isEmpty())
28                 curMin = minStack.peek();
29             else curMin = Integer.MAX_VALUE;
30  
31         }
32     }
33 
34     public int top() {
35         return stack.peek();
36         
37     }
38 
39     public int getMin() {
40         return curMin;        
41     }
42 }

 

posted @ 2014-11-29 02:51  LiBlog  阅读(174)  评论(0)  编辑  收藏  举报