# 2018q1 Homework (quiz4)
###### tags: `linyunwen` `raygoah`
contributed by <`LinYunWen`, `raygoah`>
- ==[Linked List 練習題](https://hackmd.io/s/SyK-WApKM)==
- [參考解題錄影](https://www.youtube.com/watch?v=zaA9jzWvMlg&list=PLFSyL7YoFilT_HugG5YUnSqslvFrwuIEp)
### Q1. 分析以下程式碼，推敲 FuncA, FuncB, FuncC 的作用，並且推測程式執行結果。
- 首先看到 struct node 為節點的結構，有一個 int 儲存資料，及一個 next pointer, prev pointer，因此可以推測其為一個雙向的 linked list
```cpp
struct node {
int data;
struct node *next, *prev;
};
```
#### 1. FuncA 的作用是?
```cpp=
void FuncA(struct node **start, int value) {
if (!*start) {
struct node *new_node = malloc(sizeof(struct node));
new_node->data = value;
new_node->next = new_node->prev = new_node;
*start = new_node;
return;
}
struct node *last = (*start)->prev;
struct node *new_node = malloc(sizeof(struct node));
new_node->data = value;
new_node->next = *start;
(*start)->prev = new_node;
new_node->prev = last;
last->next = new_node;
}
```
- 首先可以看到一開始的 if 為判斷 ```*start``` 存不存在是不是 ``NULL`` ，如果是 ``NULL`` 則在第 3 行 malloc 出 ```*new_node``` ，並且將其 data 放 value (#4)，然後 next, prev 都指向自己，就如下所示
:::warning
- The macro NULL is defined in <stddef.h> (and other headers) as a null pointer constant [7.19]
> Use `NULL` to indicate the macro defined in <stdlib.h> and when discussing pointers.
- Reference: [C11 spec (ISO/IEC 9899:201x)](http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1548.pdf)、[null and NULL: is there any difference?](https://bytes.com/topic/c/answers/213240-null-null-there-any-difference)
:::
```graphviz
digraph structs {
node[shape=record]
struct0 [label= "<start>start"]
struct1 [label="<prev> prev|<data> data|<next> next"];
struct0:start -> struct1:data[arrowhead=vee, tailclip=true, arrowsize=1];
struct1:prev -> struct1[arrowhead=vee, tailclip=true, arrowsize=1];
struct1:next -> struct1[arrowhead=vee, tailclip=true, arrowsize=1];
}
```
- 這是為了避免 `*start` 一開始的輸入為 ``NULL`` ，所以拿掉的話就會出錯 ```程式記憶體區段錯誤 (core dumped)```
- 再來接下看，跟 if 裡做得很像，不同點唯有 \#12~\#15 ，其是將 new_node 的 next 指向 `*start`，而將 `*start` 的 prev 指向 new_node 最後再將 last 的 next 指向 new_node，過程就有點像是
```graphviz
digraph structs {
rankdir=LR;
node[shape=box];
struct0 [label= "start"];
struct1 [label= "last"];
struct2 [label= "node1"];
struct3 [label= "node2"];
struct4 [label= "node3"];
{
rank="same";
struct0 -> struct2
}
{
rank="same";
struct1 -> struct4
}
struct2 -> struct3[arrowhead=vee, dir=both, tailclip=true, arrowsize=1];
struct3 -> struct4[arrowhead=vee, dir=both, tailclip=true, arrowsize=1];
struct4 -> struct2[arrowhead=vee, dir=both, tailclip=true, arrowsize=1];
}
```
```cpp
#12 new_node->next = *start;
```
```graphviz
digraph structs {
node[shape=record];
struct5 [label="<prev>prev|<data>new node|<next>next",color=purple]
rankdir=LR;
node[shape=box];
struct0 [label= "start"];
struct1 [label= "last"];
struct2 [label= "node1"];
struct3 [label= "node2"];
struct4 [label= "node3"];
{
rank="same";
struct0 -> struct2
}
{
rank="same";
struct1 -> struct4
}
struct2 -> struct3[arrowhead=vee, dir=both, tailclip=true, arrowsize=1];
struct3 -> struct4[arrowhead=vee, dir=both, tailclip=true, arrowsize=1];
struct4 -> struct2[arrowhead=vee, dir=both, tailclip=true, arrowsize=1];
struct5:next -> struct2 [color=red];
}
```
```cpp
#13 (*start)->prev = new_node;
```
```graphviz
digraph structs {
node[shape=record];
struct5 [label="<prev>prev|<data>new node|<next>next"]
rankdir=LR;
node[shape=box];
struct0 [label= "start"];
struct1 [label= "last"];
struct2 [label= "node1"];
struct3 [label= "node2"];
struct4 [label= "node3"];
{
rank="same";
struct0 -> struct2
}
{
rank="same";
struct1 -> struct4
}
struct2 -> struct3[arrowhead=vee, dir=both, tailclip=true, arrowsize=1];
struct3 -> struct4[arrowhead=vee, dir=both, tailclip=true, arrowsize=1];
struct4 -> struct2[arrowhead=vee, tailclip=true, arrowsize=1];
struct5:next -> struct2;
struct2->struct5:data[color=red]
}
```
```cpp
#14 new_node->prev = last;
```
```graphviz
digraph structs {
node[shape=record];
struct5 [label="<prev>prev|<data>new node|<next>next"]
rankdir=LR;
node[shape=box];
struct0 [label= "start"];
struct1 [label= "last"];
struct2 [label= "node1"];
struct3 [label= "node2"];
struct4 [label= "node3"];
{
rank="same";
struct0 -> struct2
}
{
rank="same";
struct1 -> struct4
}
struct2 -> struct3[arrowhead=vee, dir=both, tailclip=true, arrowsize=1];
struct3 -> struct4[arrowhead=vee, dir=both, tailclip=true, arrowsize=1];
struct4 -> struct2[arrowhead=vee, tailclip=true, arrowsize=1];
struct5:next -> struct2;
struct2->struct5:data
struct5:prev -> struct4[color=red]
}
```
```cpp
#15 last->next = new_node;
```
```graphviz
digraph structs {
node[shape=record];
struct5 [label="<prev>prev|<data>new \n node|<next>next"]
rankdir=LR;
node[shape=box];
struct0 [label= "start"];
struct1 [label= "last"];
struct2 [label= "node1"];
struct3 [label= "node2"];
struct4 [label= "node3"];
{
rank="same";
struct0 -> struct2
}
{
rank="same";
struct1 -> struct4
}
struct2 -> struct3[arrowhead=vee, dir=both, tailclip=true, arrowsize=1];
struct3 -> struct4[arrowhead=vee, dir=both, tailclip=true, arrowsize=1];
struct4 -> struct5:data[arrowhead=vee, tailclip=true, arrowsize=1,color=red];
struct5:next -> struct2;
struct2 -> struct5:data
struct5:prev -> struct4
}
```
將上圖最後的順序整理一下，變成如下所示：
```graphviz
digraph structs {
rankdir=LR;
node[shape=box];
struct0 [label= "start"];
struct1 [label= "last"];
struct2 [label= "node1"];
struct3 [label= "node2"];
struct4 [label= "node3"];
struct5 [label="new node"]
{
rank="same";
struct0 -> struct2
}
{
rank="same";
struct1 -> struct4
}
struct2 -> struct3[arrowhead=vee, dir=both, tailclip=true, arrowsize=1];
struct3 -> struct4[arrowhead=vee, dir=both, tailclip=true, arrowsize=1];
struct4 -> struct5[arrowhead=vee, dir=both, tailclip=true, arrowsize=1];
struct5 -> struct2[arrowhead=vee, dir=both, tailclip=true, arrowsize=1];
}
```
* 在這裡 last 指標並未更新，仍舊指向未增加新節點時的最後一個 node，而加入了新節點後，可以看到新節點會加在 linked list 尾端，也就是 last 指標指到的節點的下一個
- 因此可以得知這是個環狀雙向 linked list ，而且可以看到是從後端新增一個 node 插入， FuncA 中所做的事為 (e) 建立新節點，內容是 value，並安插在結尾
```cpp=
// q1.1
FuncA(&start, 1);
FuncA(&start, 2);
FuncA(&start, 3);
FuncA(&start, 4);
display(start);
// output
// Traversal in forward direction
// 1 2 3 4
// Traversal in reverse direction
// 4 3 2 1
```
#### 2. FuncB 的作用是?
```cpp=
void FuncB(struct node **start, int value) {
struct node *last = (*start)->prev;
struct node *new_node = malloc(sizeof(struct node));
new_node->data = value;
new_node->next = *start;
new_node->prev = last;
last->next = (*start)->prev = new_node;
*start = new_node;
}
```
- 而 FuncB 跟 FuncA 有點類似，都是建立一個新的 node (\#3) ， 給定 data 為 value (\#4) ， 主要差別是在 \#8 ，最後會將 *start 移到新的 node
```graphviz
digraph structs {
node[shape=record];
struct5 [label="<prev>prev|<data>new \n node|<next>next"]
rankdir=LR;
node[shape=box];
struct0 [label= "start"];
struct1 [label= "last"];
struct2 [label= "node1"];
struct3 [label= "node2"];
struct4 [label= "node3"];
{
rank="same";
struct0 -> struct2
}
{
rank="same";
struct1 -> struct4
}
struct2 -> struct3[arrowhead=vee, dir=both, tailclip=true, arrowsize=1];
struct3 -> struct4[arrowhead=vee, dir=both, tailclip=true, arrowsize=1];
struct4 -> struct5:data[arrowhead=vee, tailclip=true, arrowsize=1];
struct5:next -> struct2;
struct2 -> struct5:data
struct5:prev -> struct4
}
```
```cpp
#8 *start = new_node;
```
```graphviz
digraph structs {
rankdir=LR;
node[shape=box];
struct5 [label="new node"]
struct0 [label= "start", color=blue];
struct1 [label= "last"];
struct2 [label= "node1"];
struct3 [label= "node2"];
struct4 [label= "node3"];
{
rank="same";
struct0 -> struct5 [color=blue]
}
{
rank="same";
struct1 -> struct4
}
struct2 -> struct3[arrowhead=vee, dir=both, tailclip=true, arrowsize=1];
struct3 -> struct4[arrowhead=vee, dir=both, tailclip=true, arrowsize=1];
struct4 -> struct5[arrowhead=vee, dir=both, tailclip=true, arrowsize=1];
struct5 -> struct2[arrowhead=vee, dir=both, tailclip=true, arrowsize=1];
}
```
- 因此可以知道 FuncB 是建立一個新的 node 並且將其插入到開頭
```cpp=
// q1.2
FuncA(&start, 1);
FuncB(&start, 2);
FuncB(&start, 3);
FuncB(&start, 4);
display(start);
// output
// Traversal in forward direction
// 4 3 2 1
// Traversal in reverse direction
// 1 2 3 4
```
3. FuncC 的作用是?
```clike=
void FuncC(struct node **start, int value1, int value2) {
struct node *new_node = malloc(sizeof(struct node));
new_node->data = value1;
struct node *temp = *start;
while (temp->data != value2)
temp = temp->next;
struct node *next = temp->next;
temp->next = new_node;
new_node->prev = temp;
new_node->next = next;
next->prev = new_node;
}
```
- 要注意的是 \#4~\#6 有一個 while loop 要找 temp->data 如果等於 value2 時，便跳出迴圈，並且以這個 temp node 向後接上 new_node
- 因此可以知道，在 FuncC 中所做的，是將值為 value1 的 node，插入在值為 value2 的 node 後面
```cpp=
// q1.3
FuncA(&start, 1);
FuncA(&start, 2);
FuncA(&start, 3);
FuncA(&start, 4);
FuncC(&start, 5, 3);
display(start);
// output
// Traversal in forward direction
// 1 2 3 5 4
// Traversal in reverse direction
// 4 5 3 2 1
```
4. 在程式輸出中，訊息 Traversal in forward direction 後依序印出哪幾個數字呢？
```cpp=
// q1.4~10
struct node *start = NULL; // *statr -> NULL
FuncA(&start, 51); // *statr -> 51
FuncB(&start, 48); // *statr -> 48 -> 51
FuncA(&start, 72); // *statr -> 48 -> 51 -> 72
FuncA(&start, 86); // *statr -> 48 -> 51 -> 72 -> 86
FuncC(&start, 63, 51); // *statr -> 48 -> 51 -> 63 -> 72 -> 86
display(start);
```
```graphviz
digraph structs {
rankdir=LR;
node[shape=box];
struct0 [label= "start"];
struct1 [label= "48"];
struct2 [label= "51"];
struct3 [label= "63"];
struct4 [label= "72"];
struct5 [label= "86"];
{
rank="same";
struct0 -> struct1
}
struct1 -> struct2 -> struct3->struct4 -> struct5[arrowhead=vee, dir=both, tailclip=true, arrowsize=1];
struct5 -> struct1[arrowhead=vee, dir=both, tailclip=true, arrowsize=1];
}
```
- 依序為 48 -> 51 -> 63 -> 72 -> 86
:::info
延伸題目：
* 在上述 doubly-linked list 實作氣泡排序和合併排序，並提出需要額外實作哪些函式才足以達成目標
:notes: 參考實作
* [merge sort](https://github.com/LinYunWen/c-review/blob/master/week4/merge_sort.c)
* [bubble sort](https://github.com/LinYunWen/c-review/blob/master/week4/bubble_sort.c) (實作有錯誤)
:::
### Q2 考慮以下程式碼，推敲程式作用並分析輸出。
```cpp=
#include <stdio.h>
#include <stdlib.h>
/* Link list node */
struct node {
int data;
struct node *next;
};
int FuncX(struct node *head, int *data) {
struct node *node;
for (node = head->next; node && node != head; node = node->next)
data++;
return node - head;
}
struct node *node_new(int data) {
struct node *temp = malloc(sizeof(struct node));
temp->data = data; temp->next = NULL;
return temp;
}
int main() {
int count = 0;
struct node *head = node_new(0);
head->next = node_new(1);
head->next->next = node_new(2);
head->next->next->next = node_new(3);
head->next->next->next->next = node_new(4);
printf("K1 >> %s\n", FuncX(head, &count) ? "Yes" : "No");
head->next->next->next->next = head;
printf("K2 >> %s\n", FuncX(head, &count) ? "Yes" : "No");
head->next->next->next->next->next = head->next;
printf("K3 >> %s\n", FuncX(head, &count) ? "Yes" : "No");
head->next = head->next->next->next->next->next->next->next->next;
printf("K4 >> %s\n", FuncX(head, &count) ? "Yes" : "No");
printf("K5 >> %d\n", head->next->data);
printf("count >> %d\n", count);
return 0;
}
```
#### 1. FuncX 的作用是 (涵蓋程式執行行為的正確描述最多者)?
```cpp=
int FuncX(struct node *head, int *data) {
struct node *node;
for (node = head->next; node && node != head; node = node->next)
(*data)++;
return node - head;
}
```
- 可以看到這裡有個 for loop 用來從 linked list 頭跑到最後，而且注意到這個 node 是宣告在外面，所以最後跑完時， for loop 的終止條件 為 ```node && node != head``` ，表示最後結束時，node 要不是為 ``NULL`` 就是跟 head 相同，因此最後 ```node - head``` 要是為 0 的話，就是一個環狀的 linked list
#### 2. K1 >> 後面接的輸出為何
#### 3. K2 >> 後面接的輸出為何
#### 4. K3 >> 後面接的輸出為何
#### 5. K4 >> 後面接的輸出為何
#### 6. K5 >> 後面接的輸出為何
#### 7. count >> 後面接的輸出為何
#### 依照順序建立 linked list
I.
```cpp
#25 struct node *head = node_new(0);
```
```graphviz
digraph linkedlist {
rankdir=LR;
node [shape=record];
a [label="{ <data> head | <ref> }", width=1.2]
b [label="{ <data> 0 | <ref> }"];
c [label="{ <data> NULL}"];
a:ref:c -> b:data [arrowhead=vee, arrowtail=dot, dir=both, tailclip=false, arrowsize=1.2];
b:ref:c -> c:data [arrowhead=vee, arrowtail=dot, dir=both, tailclip=false];
}
```
II.
```cpp
#26 head->next = node_new(1);
```
```graphviz
digraph linkedlist {
rankdir=LR;
node [shape=record];
a [label="{ <data> head | <ref> }", width=1.2]
b [label="{ <data> 0 | <ref> }"];
c [label="{ <data> 1 | <ref> }"];
d [label="{ <data> NULL}"];
a:ref:c -> b:data [arrowhead=vee, arrowtail=dot, dir=both, tailclip=false, arrowsize=1.2];
b:ref:c -> c:data [arrowhead=vee, arrowtail=dot, dir=both, tailclip=false];
c:ref:c -> d [arrowhead=vee, arrowtail=dot, dir=both, tailclip=false];
}
```
III.
```cpp
#27 head->next->next = node_new(2);
```
```graphviz
digraph linkedlist {
rankdir=LR;
node [shape=record];
a [label="{ <data> head | <ref> }", width=1.2]
b [label="{ <data> 0 | <ref> }"];
c [label="{ <data> 1 | <ref> }"];
d [label="{ <data> 2 | <ref> }"];
e [label="{ <data> NULL}"];
a:ref:c -> b:data [arrowhead=vee, arrowtail=dot, dir=both, tailclip=false, arrowsize=1.2];
b:ref:c -> c:data [arrowhead=vee, arrowtail=dot, dir=both, tailclip=false];
c:ref:c -> d:data [arrowhead=vee, arrowtail=dot, dir=both, tailclip=false];
d:ref:c -> e [arrowhead=vee, arrowtail=dot, dir=both, tailclip=false];
}
```
IV.
```cpp
#28 head->next->next->next = node_new(3);
```
```graphviz
digraph linkedlist {
rankdir=LR;
node [shape=record];
a [label="{ <data> head | <ref> }", width=1.2]
b [label="{ <data> 0 | <ref> }"];
c [label="{ <data> 1 | <ref> }"];
d [label="{ <data> 2 | <ref> }"];
e [label="{ <data> 3 | <ref> }"];
f [label="{ <data> NULL}"];
a:ref:c -> b:data [arrowhead=vee, arrowtail=dot, dir=both, tailclip=false, arrowsize=1.2];
b:ref:c -> c:data [arrowhead=vee, arrowtail=dot, dir=both, tailclip=false];
c:ref:c -> d:data [arrowhead=vee, arrowtail=dot, dir=both, tailclip=false];
d:ref:c -> e:data [arrowhead=vee, arrowtail=dot, dir=both, tailclip=false];
e:ref:c -> f [arrowhead=vee, arrowtail=dot, dir=both, tailclip=false];
}
```
V.
```cpp
#29 head->next->next->next->next = node_new(4);
```
```graphviz
digraph linkedlist {
rankdir=LR;
node [shape=record];
a [label="{ <data> head | <ref> }", width=1.2]
b [label="{ <data> 0 | <ref> }"];
c [label="{ <data> 1 | <ref> }"];
d [label="{ <data> 2 | <ref> }"];
e [label="{ <data> 3 | <ref> }"];
f [label="{ <data> 4 | <ref> }"];
g [label="{ <data> NULL}"];
a:ref:c -> b:data [arrowhead=vee, arrowtail=dot, dir=both, tailclip=false, arrowsize=1.2];
b:ref:c -> c:data [arrowhead=vee, arrowtail=dot, dir=both, tailclip=false];
c:ref:c -> d:data [arrowhead=vee, arrowtail=dot, dir=both, tailclip=false];
d:ref:c -> e:data [arrowhead=vee, arrowtail=dot, dir=both, tailclip=false];
e:ref:c -> f:data [arrowhead=vee, arrowtail=dot, dir=both, tailclip=false];
f:ref:c -> g [arrowhead=vee, arrowtail=dot, dir=both, tailclip=false];
}
```
VI.
- K1 因為此 linked list 不為環狀，所以 FuncX 回傳 非 0 值，故輸出 ```Yes```
```graphviz
digraph linkedlist {
rankdir=LR;
node [shape=record];
a [label="{ <data> head | <ref> }", width=1.2]
b [label="{ <data> 0 | <ref> }"];
c [label="{ <data> 1 | <ref> }"];
d [label="{ <data> 2 | <ref> }"];
e [label="{ <data> 3 | <ref> }"];
f [label="{ <data> 4 | <ref> }"];
g [label="{ <data> NULL}"];
a:ref:c -> b:data [arrowhead=vee, arrowtail=dot, dir=both, tailclip=false, arrowsize=1.2];
b:ref:c -> c:data [arrowhead=vee, arrowtail=dot, dir=both, tailclip=false];
c:ref:c -> d:data [arrowhead=vee, arrowtail=dot, dir=both, tailclip=false];
d:ref:c -> e:data [arrowhead=vee, arrowtail=dot, dir=both, tailclip=false];
e:ref:c -> f:data [arrowhead=vee, arrowtail=dot, dir=both, tailclip=false];
f:ref:c -> g [arrowhead=vee, arrowtail=dot, dir=both, tailclip=false];
}
```
VII.
```cpp
#31 head->next->next->next->next = head;
```
```graphviz
digraph linkedlist {
rankdir=LR;
node [shape=record];
a [label="{ <data> head | <ref> }", width=1.2]
b [label="{ <data> 0 | <ref> }"];
c [label="{ <data> 1 | <ref> }"];
d [label="{ <data> 2 | <ref> }"];
e [label="{ <ref>|<data> 3 }"];
a:ref:c -> b:data [arrowhead=vee, arrowtail=dot, dir=both, tailclip=false, arrowsize=1.2];
b:ref:c -> c:data [arrowhead=vee, arrowtail=dot, dir=both, tailclip=false];
c:ref:c -> d:data [arrowhead=vee, arrowtail=dot, dir=both, tailclip=false];
d:ref:c -> e:data [arrowhead=vee, arrowtail=dot, dir=both, tailclip=false];
e:ref:c -> b:data [arrowhead=vee, arrowtail=dot, dir=both, tailclip=false];
}
```
VIII.
- K2 因為變成環狀，所以輸出會是 ```No```
```graphviz
digraph linkedlist {
rankdir=LR;
node [shape=record];
a [label="{ <data> head | <ref> }", width=1.2]
b [label="{ <data> 0 | <ref> }"];
c [label="{ <data> 1 | <ref> }"];
d [label="{ <data> 2 | <ref> }"];
e [label="{ <ref>|<data> 3 }"];
a:ref:c -> b:data [arrowhead=vee, arrowtail=dot, dir=both, tailclip=false, arrowsize=1.2];
b:ref:c -> c:data [arrowhead=vee, arrowtail=dot, dir=both, tailclip=false];
c:ref:c -> d:data [arrowhead=vee, arrowtail=dot, dir=both, tailclip=false];
d:ref:c -> e:data [arrowhead=vee, arrowtail=dot, dir=both, tailclip=false];
e:ref:c -> b:data [arrowhead=vee, arrowtail=dot, dir=both, tailclip=false];
}
```
IX.
```cpp
#33 head->next->next->next->next->next = head->next;
```
```graphviz
digraph linkedlist {
rankdir=LR;
node [shape=record];
a [label="{ <data> head | <ref> }", width=1.2]
b [label="{ <data> 0 | <ref> }"];
c [label="{ <data> 1 | <ref> }"];
d [label="{ <data> 2 | <ref> }"];
e [label="{ <ref>|<data> 3 }"];
a:ref:c -> b:data [arrowhead=vee, arrowtail=dot, dir=both, tailclip=false, arrowsize=1.2];
b:ref:c -> c:data [arrowhead=vee, arrowtail=dot, dir=both, tailclip=false];
c:ref:c -> d:data [arrowhead=vee, arrowtail=dot, dir=both, tailclip=false];
d:ref:c -> e:data [arrowhead=vee, arrowtail=dot, dir=both, tailclip=false];
e:ref:c -> b:data [arrowhead=vee, arrowtail=dot, dir=both, tailclip=false];
}
```
X.
- K3 還是環狀的，所以輸出會是 ```No```
```graphviz
digraph linkedlist {
rankdir=LR;
node [shape=record];
a [label="{ <data> head | <ref> }", width=1.2]
b [label="{ <data> 0 | <ref> }"];
c [label="{ <data> 1 | <ref> }"];
d [label="{ <data> 2 | <ref> }"];
e [label="{ <ref>|<data> 3 }"];
a:ref:c -> b:data [arrowhead=vee, arrowtail=dot, dir=both, tailclip=false, arrowsize=1.2];
b:ref:c -> c:data [arrowhead=vee, arrowtail=dot, dir=both, tailclip=false];
c:ref:c -> d:data [arrowhead=vee, arrowtail=dot, dir=both, tailclip=false];
d:ref:c -> e:data [arrowhead=vee, arrowtail=dot, dir=both, tailclip=false];
e:ref:c -> b:data [arrowhead=vee, arrowtail=dot, dir=both, tailclip=false];
}
```
XI.
```cpp
#35 head->next = head->next->next->next->next->next->next->next->next;
```
```graphviz
digraph linkedlist {
rankdir=LR;
node [shape=record];
a [label="{ <data> head | <ref> }", width=1.2]
b [label="{ <data> 0 | <ref> }"];
a:ref:c -> b:data [arrowhead=vee, arrowtail=dot, dir=both, tailclip=false, arrowsize=1.2];
b:ref:c -> b:data [arrowhead=vee, arrowtail=dot, dir=both, tailclip=false];
}
```
XII.
- K4 還是環狀的，所以輸出會是 ```No```
- 這邊要注意到，因為 FuncX(head, &count) 傳入 count 的記憶體位址，但是在 FuncX 中，做的是 ```data++``` 而不是 ```(*data)++``` ，因此並不會實際計算走訪的 node，所以最後離開 FuncX 後 count 值仍為 0
:::info
- 根據定義，suffix increment 的 precedence 是 1 ，而 dereference 的 precedence 是 2
- 所以可以發現的是 data++ 是將一個指向 int 的位址加一，預期應該要是 int 的值加一，因此加上 * ， 但是因為優先度的關係， *data++ 其實是 *(data++) ，還是去增加他的位址而已，故如果要增加其值，應該寫為 (*data)++
- 同時以 code 實際操作，果然跟推測結果一樣，如下所示:
```cpp=
#include <stdio.h>
#include <stdlib.h>
int main(){
int count = 100;
int count_2 = 100;
int count_3 = 100;
int *data = &count;
int *data_2 = &count_2;
int *data_3 = &count_3;
data++;
printf("data++ >> %d\n",count);
*data_2++;
printf("*data_2++ >> %d\n",count_2);
(*data_3)++;
printf("(*data_3)++ >> %d\n",count_3);
return 0;
}
```
* 輸出結果:
```
$ gcc -o test test.c
$ ./test
data++ >> 100
*data_2++ >> 100
(*data_3)++ >> 101
```
:::
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