Leetcode学习笔记：#1026. Maximum Difference Between Node and Ancestor
Given the root of a binary tree, find the maximum value V for which there exists different nodes A and B where V = |A.val - B.val| and A is an ancestor of B.
(A node A is an ancestor of B if either: any child of A is equal to B, or any child of A is an ancestor of B.)
实现：
public int maxAncestorDiff(TreeNode root) {
return dfs(root, root.val, root.val);
}
public int dfs(TreeNode root, int mn, int mx) {
if (root == null) return mx - mn;
mx = Math.max(mx, root.val);
mn = Math.min(mn, root.val);
return Math.max(dfs(root.left, mn, mx), dfs(root.right, mn, mx));
}
思路：
保存二叉树的最大值和最小值，遍历二叉树直到遇到null节点返回最大差值