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 {
Stack<Integer> stack = new Stack<>();
Stack<Integer> minStack = new Stack<>();
public void push(int x) {
stack.push(x);
if (minStack.isEmpty() || minStack.peek() >= x) {
minStack.push(x);
}
}
public void pop() {
if (stack.pop()==minStack.peek()) minStack.pop();
}
public int top() {
return stack.peek();
}
public int getMin() {
return minStack.peek();
}
}