My Python 3 code with a customized binary search tree. Passed all the tess. I know in the worst case, this is O(n^2). But in most cases, it is like O(n log n), if the tree is somewhat balanced.

class Node: def init(self, key): self.left = None self.right = None self.val = key

def minimumLoss(price): # Write your code here

min_loss = float('inf')

root = Node(price[0])
prev = root

for p in price:

    current = root

    while True:

        if current is None:
            if p > prev.val:
                prev.right = Node(p)
                break
            elif p < prev.val:
                prev.left = Node(p)
                break
        elif current.val == p:
            break
        elif current.val < p:
            prev = current
            current = current.right
        elif current.val > p:
            prev = current
            min_loss = min(min_loss, current.val - p)
                                            current = current.left

return min_loss