剑指offer题目-重建二叉树

*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。
题解：

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

public class Solution {
    public TreeNode reConstructBinaryTree(int [] pre,int [] in) {

        int length = pre.length;
        if (length == 0){
            return  null;
        }
        TreeNode treeNode = new TreeNode(pre[0]);
        int index = getIndexByValue(in,pre[0]);
        if (index != 0){
            treeNode.left = reConstructBinaryTree(Arrays.copyOfRange(pre,1,index+1),Arrays.copyOfRange(in,0,index));
        }
        if (index != length){
            treeNode.right = reConstructBinaryTree(Arrays.copyOfRange(pre,index +1,length),Arrays.copyOfRange(in,index +1,length));
        }
        return treeNode;

    }
    private int getIndexByValue(int [] array,int value){
        for (int i = 0;i<array.length;i++){
            if (array[i] == value){
                return i;
            }
        }
        return -1;
    }
}