二叉树530|501

530二叉搜索树的最小绝对差

# 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 __init__(self):
        self.result = float('inf')
        self.pre = None
    def getMinimumDifference(self, root: Optional[TreeNode]) -> int:
        self.traversal(root)
        return self.result
    def traversal(self, node) -> int:
        if not node:
            return
        cur = node
        self.traversal(cur.left)
        if self.pre:
            self.result = min(self.result, cur.val - self.pre.val)
        self.pre = cur
        self.traversal(cur.right)

501二叉搜索树中的众数

# 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 __init__(self):
        self.count = 0
        self.max_count = 0
        self.result = []
        self.pre = None

    def findMode(self, root: Optional[TreeNode]) -> List[int]:
        self.traversal(root)
        return self.result

    def traversal(self, node) -> List:
        if not node:
            return
        cur = node
        self.traversal(cur.left)
        if not self.pre:
            self.count = 1
        elif self.pre.val == cur.val:
            self.count += 1
        else:
            self.count = 1
        self.pre = cur
        
        if self.count == self.max_count:
            self.result.append(cur.val)
        elif self.count > self.max_count:
            self.max_count = self.count
            self.result = [cur.val]
        
        self.traversal(cur.right)