lintcode619- Binary Tree Longest Consecutive Sequence III- medium

It's follow up problem for Binary Tree Longest Consecutive Sequence II

Given a k-ary tree, find the length of the longest consecutive sequence path.
The path could be start and end at any node in the tree

xample

An example of test data: k-ary tree 5<6<7<>,5<>,8<>>,4<3<>,5<>,3<>>>, denote the following structure:

     5
   /   
  6     4
 /|   /|
7 5 8 3 5 3

Return 5, // 3-4-5-6-7

分治法+全局变量监控。这题只是数据结构改变了，子方法和上面的是一样的。找root+子树的最长increase与最长decrease，加起来-1就是本层的最长root了。

/**
 * Definition for a multi tree node.
 * public class MultiTreeNode {
 *     int val;
 *     List<TreeNode> children;
 *     MultiTreeNode(int x) { val = x; }
 * }
 */
public class Solution {
    /**
     * @param root the root of k-ary tree
     * @return the length of the longest consecutive sequence path
     */
     
    private int longestConsec = Integer.MIN_VALUE;
    
    private class ResultType {
        int incrs;
        int decrs;
        public ResultType(int incrs, int decrs) {
            this.incrs = incrs;
            this.decrs = decrs;
        }
    }
    
    public int longestConsecutive3(MultiTreeNode root) {
        // Write your code here
        if (root == null) {
            return 0;
        }
        helper(root);
        return longestConsec;
    }
    
    private ResultType helper(MultiTreeNode root) {
        
        List<MultiTreeNode> children = root.children;
        int crtIncrs = 1;
        int crtDecrs = 1;
        
        for (MultiTreeNode child : children) {
            ResultType childResult = helper(child);
            if (root.val + 1 == child.val) {
                crtIncrs = Math.max(1 + childResult.incrs, crtIncrs);
            }
            if (root.val - 1 == child.val) {
                crtDecrs = Math.max(1 + childResult.decrs, crtDecrs);
            }
        }
        
        if (crtIncrs + crtDecrs - 1 > longestConsec) {
            longestConsec = crtIncrs + crtDecrs - 1;
        }
        
        return new ResultType(crtIncrs, crtDecrs);
    }
}