重建二叉树【牛客网】

题目描述
输入某二叉树的前序遍历和中序遍历的结果，请重建出该二叉树。假设输入的前序遍历和中序遍历的结果中都不含重复的数字。例如输入前序遍历序列{1,2,4,7,3,5,6,8}和中序遍历序列{4,7,2,1,5,3,8,6}，则重建二叉树并返回。

/**
 * Definition for binary tree
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
import java.util.*;

public class Solution {
    public TreeNode reConstructBinaryTree(int [] pre,int [] in) {
        if(pre.length == 0 || in.length == 0) {
            return null;
        }
        TreeNode root = new TreeNode(pre[0]);
        for(int i = 0; i<in.length;i++) {
            if(in[i] == pre[0]) {
                // 递归获取左节点
                root.left = reConstructBinaryTree(
                    Arrays.copyOfRange(pre, 1, i+1), 
                    Arrays.copyOfRange(in, 0, i));
                // 递归获取右节点
                root.right = reConstructBinaryTree(
                    Arrays.copyOfRange(pre, i+1, pre.length),
                    Arrays.copyOfRange(in, i+1, in.length));
            }
        }
        return root;
    }
}