树：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) {
        TreeNode root = reConstructBinaryTree(pre, 0, pre.length - 1, in, 0,
                in.length - 1);
        return root;
    }

    // 前序遍历{1,2,4,7,3,5,6,8}和中序遍历序列{4,7,2,1,5,3,8,6}
    private TreeNode reConstructBinaryTree(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 = reConstructBinaryTree(pre, startPre + 1, startPre
                        + i - startIn, in, startIn, i - 1);
                root.right = reConstructBinaryTree(pre, i - startIn + startPre
                        + 1, endPre, in, i + 1, endIn);
            }

        return root;
    }
}