leetcode 671 Second Minimum Node In a Binary Tree

Java

class Solution {
public int findSecondMinimumValue(TreeNode root) {
if(root==null) return -1;
if(root.left==null && root.right==null) return -1;

int left=root.left.val;
int right=root.right.val;

if(root.left.val==root.val){
left = findSecondMinimumValue(root.left);
}
if(root.right.val==root.val){
right = findSecondMinimumValue(root.right);
}
if(left!=-1&&right!=-1) return Math.min(left,right);
else if(left==-1) return right;
else return left;
}
}Python
class Solution:
def findSecondMinimumValue(self, root):
"""
:type root: TreeNode
:rtype: int
"""
if not root:
return -1
if not root.left and not root.right:
return -1

left,right=root.left.val,root.right.val

if root.left.val==root.val:
left=self.findSecondMinimumValue(root.left)
if root.right.val==root.val:
right=self.findSecondMinimumValue(root.right)

if left==-1 or right==-1:
return -left*right
else:
return min(left,right)