LeetCode——Min Stack

题目：
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.

解答：

//辅助stack每次存最小的数值class MinStack {public:    MinStack() {        pStack = new stack<int>;        pHelpStack = new stack<int>;    }    ~MinStack() {        delete pStack;        delete pHelpStack;    }    void push(int x) {        pStack->push(x);        if (pHelpStack->empty()) {            pHelpStack->push(x);        } else if (pHelpStack->top() >= x) {            pHelpStack->push(x);        } else {            pHelpStack->push(pHelpStack->top());        }    }    void pop() {        pStack->pop();        pHelpStack->pop();    }    int top() {        return pStack->top();    }    int getMin() {        return pHelpStack->top();    }private:    stack<int>* pStack;    stack<int>* pHelpStack;};