--- tags: Linux2020 --- # 2020q3 Homework1 (quiz1) contributed by < `Ylowy` > ## Outline 1. 重新回答[第 1 周測驗題](https://hackmd.io/@sysprog/sysprog2020-quiz1)，連同附帶的「延伸問題」。 解釋程式運作原理時，應提供對應的 Graphviz 圖例，可參照 Linked List 題目 1 + 分析 2. 比照 課前測驗參考解答: Q1 和 Linked list 題目分析 的模式來撰寫共筆，需要詳細分析自己的思路、參閱的材料 (以第一手材料為主，包含 C 語言規格書的章節)，以及進行相關實驗。 ## 1. 重新回答第一周測驗題 ### tpyedef 型態先定義長這樣，很簡單的 structure ```c= typedef struct __node { int value; struct __node *next; } node_t; ``` ### add_entry ```c= void add_entry(node_t **head, int new_value) { node_t **indirect = head; node_t *new_node = malloc(sizeof(node_t)); new_node->value = new_value; new_node->next = NULL; assert(new_node); while (*indirect) indirect = &(*indirect)->next; *indirect = new_node; } ``` ### find_entry 這個比較簡單就不佳贅述了 ```c= node_t *find_entry(node_t *head, int value) { node_t *current = head; for (; current && current->value != value; current = current->next) /* interate */; return current; } ``` ### remove_entry ```c= void remove_entry(node_t **head, node_t *entry) { node_t **indirect = head; while ((*indirect) != entry) indirect = &(*indirect)->next; *indirect = entry->next; free(entry); } ``` ### swap_pair 這邊卡真久，關鍵在for迴圈中的細節 ```c= void swap_pair(node_t **head) { for (node_t **node = head; *node && (*node)->next;node = &(*node)->next->next){ node_t *tmp = *node; *node = (*node)->next; tmp->next = (*node)->next; (*node)->next = tmp; } } ``` ### reverse [Ylowy/Lab0-c](https://hackmd.io/1BvGp-2oQuqYUzD1NtZU6g?view) 參考我之前寫的 reverse queue 的方法，省一個空間 ```c= void reverse(node_t **head) { node_t * tail = *head; while(tail->next) tail = tail->next; tail->next = *head; node_t *ptr = (*head)->next->next; while ((*head)->next != tail) { (*head)->next->next = tail->next; tail->next = (*head)->next; (*head)->next = ptr; ptr = ptr->next; } tail = *head; *head = (*head)->next; tail->next = NULL; } ``` ```graphviz digraph graphname { rankdir=LR; A [label="A" color=Blue, fontcolor=Red, fontsize=24, shape=box] B [label="B" color=Blue, fontcolor=Red, fontsize=24, shape=box] C [label="C" color=Blue, fontcolor=Red, fontsize=24, shape=box] D [label="D" color=Blue, fontcolor=Red, fontsize=24, shape=box] E [label="E" color=Blue, fontcolor=Red, fontsize=24, shape=box] head[label="Head"] tail[label="Tail"] A->B [fontcolor=black] B->C [fontcolor=black] C->D [fontcolor=black] D->E [fontcolor=black] head->A [fontcolor=black] tail->E [fontcolor=black] E->NULL [fontcolor=black] } ``` q 的 Initial 1. ptr = head->next->next 2. tail->next = head ```graphviz digraph graphname { rankdir=LR; A [label="A" color=Blue, fontcolor=Red, fontsize=24, shape=box] B [label="B" color=Blue, fontcolor=Red, fontsize=24, shape=box] C [label="C" color=Blue, fontcolor=Red, fontsize=24, shape=box] D [label="D" color=Blue, fontcolor=Red, fontsize=24, shape=box] E [label="E" color=Blue, fontcolor=Red, fontsize=24, shape=box] head[label="Head"] tail[label="Tail"] ptr[label="ptr"] A->B [fontcolor=black] B->C [fontcolor=black] C->D [fontcolor=black] D->E [fontcolor=black] ptr->C [fontcolor=black] head->A [fontcolor=black] tail->E [fontcolor=black] E->A [fontcolor=black] } ``` 再來做 while(..) ```graphviz digraph graphname { rankdir=LR; A [label="A" color=Blue, fontcolor=Red, fontsize=24, shape=box] B [label="B" color=Blue, fontcolor=Red, fontsize=24, shape=box] C [label="C" color=Blue, fontcolor=Red, fontsize=24, shape=box] D [label="D" color=Blue, fontcolor=Red, fontsize=24, shape=box] E [label="E" color=Blue, fontcolor=Red, fontsize=24, shape=box] head[label="Head"] tail[label="Tail"] ptr[label="ptr"] A->C [fontcolor=black] B->A [fontcolor=black] C->D [fontcolor=black] D->E [fontcolor=black] E->B [fontcolor=black] ptr->D [fontcolor=black] head->A [fontcolor=black] tail->E [fontcolor=black] } ``` ```graphviz digraph graphname { rankdir=LR; A [label="A" color=Blue, fontcolor=Red, fontsize=24, shape=box] B [label="B" color=Blue, fontcolor=Red, fontsize=24, shape=box] C [label="C" color=Blue, fontcolor=Red, fontsize=24, shape=box] D [label="D" color=Blue, fontcolor=Red, fontsize=24, shape=box] E [label="E" color=Blue, fontcolor=Red, fontsize=24, shape=box] head[label="Head"] tail[label="Tail"] ptr[label="ptr"] A->D [fontcolor=black] B->A [fontcolor=black] C->B [fontcolor=black] D->E [fontcolor=black] E->C [fontcolor=black] ptr->E [fontcolor=black] head->A [fontcolor=black] tail->E [fontcolor=black] } ``` ```graphviz digraph graphname { rankdir=LR; A [label="A" color=Blue, fontcolor=Red, fontsize=24, shape=box] B [label="B" color=Blue, fontcolor=Red, fontsize=24, shape=box] C [label="C" color=Blue, fontcolor=Red, fontsize=24, shape=box] D [label="D" color=Blue, fontcolor=Red, fontsize=24, shape=box] E [label="E" color=Blue, fontcolor=Red, fontsize=24, shape=box] head[label="Head"] tail[label="Tail"] ptr[label="ptr"] A->E [fontcolor=black] B->A [fontcolor=black] C->B [fontcolor=black] D->C [fontcolor=black] E->D [fontcolor=black] ptr->C [fontcolor=black] head->A [fontcolor=black] tail->E [fontcolor=black] } ``` 最後做 head tail調整 ```graphviz digraph graphname { rankdir=LR; A [label="A" color=Blue, fontcolor=Red, fontsize=24, shape=box] B [label="B" color=Blue, fontcolor=Red, fontsize=24, shape=box] C [label="C" color=Blue, fontcolor=Red, fontsize=24, shape=box] D [label="D" color=Blue, fontcolor=Red, fontsize=24, shape=box] E [label="E" color=Blue, fontcolor=Red, fontsize=24, shape=box] head[label="Head"] tail[label="Tail"] A->NULL [fontcolor=black] B->A [fontcolor=black] C->B [fontcolor=black] D->C [fontcolor=black] E->D [fontcolor=black] head->E [fontcolor=black] tail->A [fontcolor=black] } ``` ## 2. 比照課前測驗參考解答
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