[Leetcode 270]Closest Binary Search Tree Value

class Solution():
    def closestValue(self, root, target):
        if root == None:
            return None 
        
        if target <= root.val:
            if root.left != None:
                closestValue_left =  self.closestValue(root.left, target)
                if root.val - target < abs(closestValue_left - target):
                    return root.val
                else:
                    return closestValue_left                
            else:
                return root.val
        else:
            if root.right != None:
                closestValue_right =  self.closestValue(root.right, target)
                if root.val - target < abs(closestValue_right - target):
                    return root.val
                else:
                    return closestValue_right               
            else:
                return root.val
            
            
            
	def closestValue2(self, root, target):
        if root == None:
            return None 
        
        ans = abs(root.val - target)
        ans_val = root.val
        
        while True:
            if abs(root.val - target) < ans:
                ans = abs(root.val - target) 
                ans_val = root.val
            
            if target < root.val and root.left:
                root = root.left
            elif target > root.val and root.right:
                root = root.right
            else:
                break 
            
        return ans_val

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