LeetCode #501: Find Mode in Binary Search Tree
β’ 251 words β’ 2 min β’ updated
LeetCode #501: Find Mode in Binary Search Tree:
Recursive DFS with a Counter:
python
from collections import Counter
# Definition for a binary tree node.
# class TreeNode:
# def __init__(self, val=0, left=None, right=None):
# self.val = val
# self.left = left
# self.right = right
class Solution:
def findMode(self, root: Optional[TreeNode]) -> List[int]:
counter = Counter()
def dfs(node):
if not node:
return
counter[node.val] += 1
dfs(node.left)
dfs(node.right)
dfs(root)
max_mode = max(counter.values())
return [k for (k, v) in counter.items() if v == max_mode]Iterative DFS:
python
from collections import Counter
# Definition for a binary tree node.
# class TreeNode:
# def __init__(self, val=0, left=None, right=None):
# self.val = val
# self.left = left
# self.right = right
class Solution:
def findMode(self, root: Optional[TreeNode]) -> List[int]:
counter = Counter()
def dfs(node):
if not node:
return
stack = [node]
while stack:
node = stack.pop()
counter[node.val] += 1
if node.left:
stack.append(node.left)
if node.right:
stack.append(node.right)
dfs(root)
max_mode = max(counter.values())
return [k for (k, v) in counter.items() if v == max_mode]BFS:
python
from collections import Counter, deque
# Definition for a binary tree node.
# class TreeNode:
# def __init__(self, val=0, left=None, right=None):
# self.val = val
# self.left = left
# self.right = right
class Solution:
def findMode(self, root: Optional[TreeNode]) -> List[int]:
counter = Counter()
def dfs(node):
if not node:
return
queue = deque([node])
while queue:
node = queue.popleft()
counter[node.val] += 1
if node.left:
queue.append(node.left)
if node.right:
queue.append(node.right)
dfs(root)
max_mode = max(counter.values())
return [k for (k, v) in counter.items() if v == max_mode]