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。

贴一张盗的图

代码

/**
 * 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) {
        return reConstructBinaryTree(pre, 0, in, 0, in.length-1);
    }
//	pre {1,2,4,7,3,5,6,8}
//	in  {4,7,2,1,5,3,8,6}
	
    private TreeNode reConstructBinaryTree(int [] pre, int preIdx, int[] in, int inL, int inR)
    {
        if( (preIdx >= pre.length) || (inL > inR) ) return null;
        int rootVal = pre[preIdx];
        TreeNode root = new TreeNode(rootVal);
        int i=0;
        for(i = inL; i <= inR; i++){
            if(rootVal == in[i]){
                break;
            }
        }
        root.left = reConstructBinaryTree(pre, preIdx+1, in, inL, i-1);
        root.right = reConstructBinaryTree(pre, preIdx+(i-inL+1), in, i+1, inR);
        return root;
    } 
}