Min Stack
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 {
List<Integer> stack = new ArrayList<Integer>();
int top = -1;
int min = Integer.MAX_VALUE;
public void push(int x) {
top++;
stack.add(x);
if(min > x){
min = x;
}
}
public void pop() {
int element = stack.remove(top--);
if(element == min)
{
updateMin();
}
}
public int top() {
int result = stack.get(top);
return result;
}
public int getMin() {
return this.min;
}
public void updateMin(){
if(top == -1)
{
min = Integer.MAX_VALUE;
return;
}
min = stack.get(0);
for(int i = 1; i <= top; i++){
if(min > stack.get(i))
min = stack.get(i);
}
}
}