CompetitiveProgramming/MinStack.java at master · hdelcampo/CompetitiveProgramming · GitHub

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class MinStack {

    Stack<Integer> elements = new Stack<>();
    Stack<Integer> mins = new Stack<>();

    /** initialize your data structure here. */
    public MinStack() {

    }

    public void push(int x) {

        elements.push(x);
        if(mins.empty() || x <= getMin()) {
            mins.push(x);
        }

    }

    public void pop() {

        if (elements.empty()) return;

        int elem = elements.pop();

        if (elem == getMin()) mins.pop();

    }

    public int top() {

        return elements.peek();

    }

    public int getMin() {

        return mins.peek();

    }
}