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。

/** * 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;    }    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;    }}