Min Stack — Parallel Min Tracking Stack

# Python
class MinStack:
    def __init__(self): self.stack = []; self.min_stack = []
    def push(self, val):
        self.stack.append(val)
        self.min_stack.append(min(val, self.min_stack[-1] if self.min_stack else val))
    def pop(self): self.stack.pop(); self.min_stack.pop()
    def top(self): return self.stack[-1]
    def getMin(self): return self.min_stack[-1]

// Java
class MinStack {
    Deque<Integer> stack = new ArrayDeque<>(), minStack = new ArrayDeque<>();
    public void push(int val) {
        stack.push(val);
        minStack.push(minStack.isEmpty() ? val : Math.min(val, minStack.peek()));
    }
    public void pop() { stack.pop(); minStack.pop(); }
    public int top() { return stack.peek(); }
    public int getMin() { return minStack.peek(); }
}

// C++
class MinStack {
    stack<int> st, mn;
public:
    void push(int val) {
        st.push(val);
        mn.push(mn.empty() ? val : min(val, mn.top()));
    }
    void pop() { st.pop(); mn.pop(); }
    int top() { return st.top(); }
    int getMin() { return mn.top(); }
};