501.二叉搜索树的众数

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode() {}
 *     TreeNode(int val) { this.val = val; }
 *     TreeNode(int val, TreeNode left, TreeNode right) {
 *         this.val = val;
 *         this.left = left;
 *         this.right = right;
 *     }
 * }
 */
class Solution {
    ArrayList<Integer> reslist =new ArrayList<>();
    int count;
    int maxcount;
    TreeNode pre; 
    public int[] findMode(TreeNode root) {
        sub_iter(root);
        int[] res = new int[reslist.size()];
        for(int i=0;i<reslist.size();i++){
            res[i] = reslist.get(i);
        }
        return res;
    }
    public void sub_iter(TreeNode node){
        if(node==null){
            return;
        }
        sub_iter(node.left);
        if(pre==null){
            count=1;
        }else if(pre.val == node.val){
            count++;
        }else{
            count=1;
        }
        pre = node;
        if(count==maxcount) reslist.add(node.val);
        if(count>maxcount){
            maxcount = count;
            reslist.clear();
            reslist.add(node.val);
        }
        sub_iter(node.right);
    }
}