Min Stack
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 element val onto 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 {
int min = Integer.MAX_VALUE;
Stack<Integer> stack = new Stack<Integer>();
public void push(int x) {
// only push the old minimum value when the current
// minimum value changes after pushing the new value x
if(x <= min){
stack.push(min);
min=x;
}
stack.push(x);
}
public void pop() {
// if pop operation could result in the changing of the current minimum value,
// pop twice and change the current minimum value to the last minimum value.
if(stack.pop() == min) min=stack.pop();
}
public int top() {
return stack.peek();
}
public int getMin() {
return min;
}
}Posted by Jamie Meyer a month ago