剑指offer_【4】重建二叉树

import java.util.Arrays;

 public class  { 
     int val; 
     TreeNode left; 
     TreeNode right; 
     TreeNode(int x) { val = x; } 
 } 
public class Solution {    
    public TreeNode reConstructBinaryTree(int [] pre,int [] in) {        
        if(pre.length==0 || in.length==0)               
            return null;           
        TreeNode node = new TreeNode(pre[0]);    //根结点       
        for(int i=0;i<pre.length;i++){      
        //找到根节点在中序遍历的点，左边为根的左节点，右边为根的右节点         
            if(pre[0] == in[i]){    
        //递归构建左子树，此时前序的范围缩小为[1,i+1),中序缩小为[0,i)              
             node.left =reConstructBinaryTree(Arrays.copyOfRange
                         (pre,1,i+1),Arrays.copyOfRange(in,0,i));
        //递归构建右子树,此时前序的范围缩小为[i+1,len),中序缩小为[i+1,len)                   
             node.right = reConstructBinaryTree(Arrays.copyOfRange
        (pre,i+1,pre.length),Arrays.copyOfRange(in,i+1,in.length));                   
                break;               
            }           
        }           
        return node;
    }
}