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.

利用另外一個棧存儲棧中的最小值

class MinStack {
public:
    stack<int> myStack;
    stack<int> minStack;
    void push(int x) {
        myStack.push(x);
        if(minStack.empty() || minStack.top()>=x)
            minStack.push(x);
    }

    void pop() {
        if(myStack.top() == minStack.top())
            minStack.pop();
        
        myStack.pop();
    }

    int top() {
        return myStack.top();
    }

    int getMin() {
        return minStack.top();
    }
};