题目:

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。

public static TreeNode reConstructBinaryTree(int[] pre, int[] in) {
        if (pre.length != in.length || pre.length == 0 || in.length == 0) {
            return null;
        }
        TreeNode root = new TreeNode(pre[0]);
        int index = -1;
        for (int i = 0; i < in.length; i++) {
            if (in[i] == pre[0]) {
                index = i;
            }
        }
        int[] subLefIn = new int[index];
        int[] subRigIn = new int[in.length - index - 1];
        for (int i = 0; i < in.length ; i++) {
            if (i < index) {
                subLefIn[i] = in[i];
            }
            if (i > index) {
                subRigIn[i - index-1] = in[i];
            }
        }
        int[] subLefPre = new int[index];
        int[] subRigPre = new int[pre.length - index - 1];
        for (int i = 1; i < pre.length; i++) {
            if (i < index+1) {
                subLefPre[i -1 ] = pre[i];
            }
            if (i >= index +1) {
                subRigPre[i - index -1 ] = pre[i];
            }
        }
        root.left = reConstructBinaryTree(subLefPre,subLefIn);
        root.right = reConstructBinaryTree(subRigPre,subRigIn);
        return root;
    }