Min Stack

标签：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.

要求构建一个能随时返回最小值的栈 所以在执行 push和pop操作时 要对最小值进行更新 代码如下：

class MinStack {
        Stack<Integer> sta=new Stack<>();
	    int min=Integer.MAX_VALUE;
	    public void push(int x) {
	        sta.push(x);
	        if(x<=min) min=x;
	    }
	    public void pop() {
	        int a=sta.peek();
	    	sta.pop();
	    	if(a==min){
	    	    min=Integer.MAX_VALUE;
	    		if(!sta.isEmpty()){
	    			for(int b:sta){
	    				if(b<=min) min=b;
	    			}
	    		}
	    	}
	    }
	    public int top() {
	        return sta.peek();
	    }

	    public int getMin() {
	        if(sta.isEmpty()) return 0;
	        else return min;
	    }
}

Min Stack

标签：stack

原文地址：http://blog.csdn.net/u012734829/article/details/42491563