Design a stack that supports push, pop, top, and retrieving the minimum element in constant time.
Implement the MinStack class:
MinStack()initializes the stack object.void push(int val)pushes the elementvalonto the stack.void pop()removes the element on the top of the stack.int top()gets the top element of the stack.int getMin()retrieves the minimum element in the stack.
You must implement a solution with O(1) time complexity for each function.
class MinStack {
Stack<StackNode> st;
class StackNode{
int current;
int currentMin;
}
public MinStack() {
st = new Stack();
}
public void push(int val) {
StackNode node1 = new StackNode();
node1.current = val;
if(!st.isEmpty()){
if(st.peek().currentMin > val){
node1.currentMin = val;
}else{
node1.currentMin = st.peek().currentMin;
}
}else{
node1.currentMin = val;
}
st.push(node1);
}
public void pop() {
st.pop();
}
public int top() {
return st.peek().current;
}
public int getMin() {
return st.peek().currentMin;
}
}