寻找BST…的最小深度findHeight函数不起作用

class TreeNode:
    def __init__(self, val=0, left=None, right=None):
        self.val = val
        self.left = left
        self.right = right

def findHeight(root):
    if not root:
        return 0
    left_height = findHeight(root.left)
    right_height = findHeight(root.right)
    return min(left_height, right_height) + 1

# 示例用法
root = TreeNode(1)
root.left = TreeNode(2)
root.right = TreeNode(3)
root.left.left = TreeNode(4)

print(findHeight(root))  # 输出: 2

def findHeightIterative(root):
    if not root:
        return 0
    
    queue = [(root, 1)]
    min_depth = float('inf')
    
    while queue:
        node, depth = queue.pop(0)
        if not node.left and not node.right:
            min_depth = min(min_depth, depth)
        if node.left:
            queue.append((node.left, depth + 1))
        if node.right:
            queue.append((node.right, depth + 1))
    
    return min_depth

# 示例用法
print(findHeightIterative(root))  # 输出: 2