2023.11.02 Today's Challenge

https://leetcode.com/problems/find-mode-in-binary-search-tree/

Find Mode in Binary Search Tree - LeetCode

DFS로 푸는 문제.
DFS에도 종류가 좀 있구만..

    def findMode(self, root: Optional[TreeNode]) -> List[int]:
        def dfs(node, counter):
            if not node:
                return
            
            counter[node.val] += 1
            dfs(node.left, counter)
            dfs(node.right, counter)

        counter = defaultdict(int)
        dfs(root, counter)
        max_freq = max(counter.values())

        ans = []

        for key in counter:
            if counter[key] == max_freq:
                ans.append(key)
        
        return ans