二叉樹------由前序和中序求後序

題目描述：已知一棵樹的前序和中序周遊結果，求其後序結果。

分析：

對于一個二叉樹而言，若知道其前序和中序，那麼就能唯一确定其後序。方法就是通過每次判斷，遞歸的得到每棵子樹。

Node* Rebuild(int *pre, int *mid, int length)
{
    if(pre == NULL || mid == NULL || length < )
        return NULL;
    return Rebuild(pre, pre + length - , mid, mid + length - );
}

Node *ReBuild(int *prestart, int *preend, int *midstart, int *midend)
{
    int rootValue = prestart[];
    Node *root = new Node;
    root->left = NULL;
    root->right = NULL;
    root->data = rootValue;

    if(prestart == preend)
    {
        if(minstart == midend && *prestart == *midstart)
            return root;
        else
            {
                printf("Invalid input!\n");
                exit();
            }
    }

    int *rootIndex = midstart;
    while(rootIndex <= midend && *rootIndex != rootValue)
        rootIndex++;
    if(rootIndex > midend)
    {
        printf("Invaild input\n");
        exit();
    }

    int leftlen = rootIndex - midstart;
    int *preleftend = prestart + leftlen;
    if(leftlen > )
    {
        root->left = Rebuild(prestart, preleftend, midstart, rootIndex - );            
    }
    if(left < midend - midstart)
    {
        root->right = Rebuild(preleftend + , preend, rootIndex + , midend);
    }

    return root;
}