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.

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.

这道题还需要重新做一下

Stack<Integer> stack = new Stack<Integer>();    Stack<Integer> minStack = new Stack<Integer>();    public MinStack() {    }    public void push(int x) {        stack.push(x);        if(minStack.isEmpty()|| x<= minStack.peek())                minStack.push(x);    }    public void pop() {      if(stack.peek().equals(minStack.peek())){          minStack.pop();      }      stack.pop();    }    public int top() {        return stack.peek();    }    public int getMin() {        return minStack.peek();    }

士大夫撒