leetcode——155—— 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.

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

    void pop() {
        if(stk.top() == min.top())
        {
            stk.pop();
            min.pop();
        }
        else
            stk.pop();
    }

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

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