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。

java

/** * 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) {        if (pre == null || pre.length == 0 || in == null || in.length == 0) {            return null;        }        return reBuild(pre, 0, pre.length - 1, in, 0, in.length - 1);    }    private TreeNode reBuild(int[] pre, int preStart, int preEnd,                             int[] in, int inStart, int inEnd) {        if (preStart > preEnd || inStart > inEnd) {            return null;        }        TreeNode root = new TreeNode(pre[preStart]);        int index = inStart;        while (index <= inEnd && pre[preStart] != in[index]) {            index++;        }        int length = index - inStart;        int leftEnd = preStart + length;        if (length > 0) {            root.left = reBuild(pre, preStart + 1, leftEnd, in, inStart, index - 1);        }        if (length < preEnd - inStart) {            root.right = reBuild(pre, leftEnd + 1, preEnd, in, index + 1, inEnd);        }        return root;    }}