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.
class MinStack {
public:
void push(int x) {
elements.push(x);
if (mins.empty()||x<=mins.top())
mins.push(x);
}
void pop() {
if (elements.empty()) return;
if (elements.top() == mins.top())
mins.pop();
elements.pop();
}
int top() {
return elements.top();
}
int getMin() {
return mins.top();
}
private:
stack<int> elements;
stack<int> mins;
};