Can someone please explain why my solution is incorrect


#1

class Solution:
# @param A : root node of tree
# @param B : integer
# @return the root node in the tree

def getSuccessor(self, A, B):
    stack = []
    stack.append(A)
    temp = A.left
    node_found = False
    while stack:
        while temp != None:
            stack.append(temp)
            temp = temp.left
        cur_node = stack.pop()
        if node_found == True:
            return cur_node
        if cur_node.val == B:
            node_found = True
        temp = cur_node.right
    return None