c语言之 *指针与 **指针

*n 一级指针：

**s 二级指针：

CHILD *walk, *next, *tmp_child, **scan;

next = walk->next
scan = &walk->next;
while (*scan) {     // *scan = walk->next
    if (!tree_equal(walk->child, (*scan)->child)) {     // (*scan)->child) = walk->next->child
        scan = &(*scan)->next;                          // &(*scan)->next = &walk->next->child
    } 
    else {
        if (next == *scan)                              // (next == *scan) ==> (next == walk->next)
            next = (*scan)->next;                       // (*scan)->next = walk->next->next
        count++;
        tmp_child = (*scan)->next;                      // (*scan)->next = walk->next->next
        free(*scan);
        *scan = tmp_child;                              // *scan = walk->next
    }
}