剑指Offer----重建二叉树

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; } * } */public class Solution {    public TreeNode reConstructBinaryTree(int [] pre,int [] in) {        int length=pre.length;        int length1=in.length;        if(pre==null||in==null||length<=0||length1<=0)return null;        return ConstructCore(pre,0,length-1,in,0,length1-1);    }    private TreeNode ConstructCore(int[] pre,int startpre,int endpre,int[] in,int startin,int endin){        if(startpre>endpre||startin>endin)return null;        TreeNode root=new TreeNode(pre[startpre]);        for(int i=startin;i<=endin;i++){            if(in[i]==pre[startpre]){                root.left=ConstructCore(pre,startpre+1,startpre+i-startin,in,startin,i-1);                root.right=ConstructCore(pre,startpre+i-startin+1,endpre,in,i+1,endin);            }        }        return root;    }}