1026. Maximum Difference Between Node and Ancestor

Link

Solution

Passing the max/min value during the DFS traversal path

    int ret = 0;
    public int maxAncestorDiff(TreeNode root) {
        dfs(root, root.val, root.val);
        
        return ret;
    }
    
    public void dfs(TreeNode node, int max, int min){        
        if(node == null) return;
        
        ret = Math.max(ret, max - node.val);
        ret = Math.max(ret, node.val - min);
        if(node.left != null){
            dfs(node.left, Math.max(max, node.left.val), Math.min(min, node.left.val));
        }
        if(node.right != null){
            dfs(node.right, Math.max(max, node.right.val), Math.min(min, node.right.val));
        }
    }