重建二叉树

/** * Definition for binary tree * public class TreeNode { *     int val; *     TreeNode left; *     TreeNode right; *     TreeNode(int x) { val = x; } * } */public class Solution {    public TreeNode reConstructBinaryTree(int [] pre,int [] in) {       if (pre == null || in == null || pre.length == 0 || in.length == 0)        {            return null;        }        TreeNode treeNode = new TreeNode(pre[0]);        // 找出in数组的分割数字，in左边的为左子树的中序遍历，右边为右子树的中序遍历        int i = 0;        while (in[i] != pre[0]) i++;        int[] preL = new int [i];        int[] inL = new int [i];        int[] preR = new int [pre.length-i-1];        int[] inR = new int [pre.length-i-1];        System.arraycopy(pre, 1, preL, 0, i);        System.arraycopy(pre, i+1, preR, 0, pre.length-i-1);        System.arraycopy(in, 0, inL, 0, i);        System.arraycopy(in, i+1, inR, 0, in.length-i-1);        treeNode.left = reConstructBinaryTree(preL, inL);        treeNode.right = reConstructBinaryTree(preR, inR);        return treeNode;    }}