Leetcode 0671 Second Minimum Node In a Binary Tree

Problem statement

https://leetcode.com/problems/second-minimum-node-in-a-binary-tree/

Solution

Just traverse our tree, using dfs or bfs.

Complexity

We have O(n) time complexity and O(h) space complexity.

Code

class Solution:
    def findSecondMinimumValue(self, root):
        self.found = float("inf")
        rootval = root.val
        
        def dfs(node):
            if node.val == rootval:
                if node.left: dfs(node.left)
                if node.right: dfs(node.right)
            else:  
                self.found = min(self.found, node.val)
                
        dfs(root)
        return self.found if self.found != float("inf") else -1