# 155.Min-Stack

## 题目地址

https://www.lintcode.com/problem/min-stack/

https://leetcode.com/problems/min-stack/

## 题目描述

``````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.

Example:
MinStack minStack = new MinStack();
minStack.push(-2);
minStack.push(0);
minStack.push(-3);
minStack.getMin();   --> Returns -3.
minStack.pop();
minStack.top();      --> Returns 0.
minStack.getMin();   --> Returns -2.``````

## 代码

``````public class Solution {
private Stack<Integer> stack1;
private Stack<Integer> stack2;
public Solution () {
stack1 = new Stack<Integer>();
stack2 = new Stack<Integer>();
}

public void push(int number) {
stack1.push(number);
if (stack2.empty()) {
stack2.push(number);
} else {
stack2.push(Math.min(number, stack2.peek()));
}
}

public int pop() {
stack2.pop();
return stack1.pop();
}

public int min() {
return stack2.peek();
}

}``````

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