[Min Stack] The std::deque version passed. Any idea why?

[ghost]

class MinStack {
public:
    void push(int x) {
        stack_.push_front(x);
        if (minStack_.empty() || x < *minStack_.front()) {
            minStack_.push_front(&stack_.front());
        }
    }
    void pop() {
        if (&stack_.front() == minStack_.front()) {
            minStack_.pop_front();
        }
        stack_.pop_front();
    }
    int top() {
        return stack_.front();
    }
    int getMin() {
        return *minStack_.front();
    }
private:
    deque<int> stack_;
    deque<int*> minStack_;
};

This puzzle really sucks for C++ programers. :-( However the OJ just provide the Java solution.

[ghost]

I view the source code of the STL (from both clang++ and g++):

std::deque uses a “split buffer” to store the pointers of the new int. And the new capacity is the double of the old one.

It's still confusing.