1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 | #include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>
#include <assert.h>
/* See append_3.c for the “best” version.
*
* This version is from office hours and uses a simpler free_list(…).
*/
typedef struct _Node {
int value;
struct _Node* next;
} Node;
void print_list(Node* head) {
for(Node* curr = head; curr != NULL; curr = curr -> next) {
printf("[%d]", curr -> value);
if(curr -> next != NULL) { // If curr is not the tail...
printf("→");
}
}
printf("\n");
}
void _append(int value, Node** a_head, Node** a_tail) {
// Do not copy this code (or any other code). Default is always no copying.
// Allocate memory on heap for a new node.
Node* new_node = malloc(sizeof(*new_node));
// Initialize fields of the new node using a COMPOUND LITERAL.
*new_node = (Node) { .value = value, .next = NULL };
// ↑ ↑
// * ⊘
if(*a_head == NULL) { // If list is empty (size=0), initialize a list of size one.
assert(*a_tail == NULL);
*a_head = new_node;
*a_tail = new_node;
assert(*a_head = *a_tail); // Size must be 1 now.
}
else {
assert(*a_head != NULL && *a_tail != NULL);
(*a_tail) -> next = new_node; // Connect tail to new node.
*a_tail = new_node; // Set tail to new node.
} // ⚠ Do not switch the order of these two steps!!!
assert(*a_head != NULL && *a_tail != NULL);
assert((*a_tail) -> value == value);
assert((*a_tail) -> next == NULL); // Tail's '.next' field must always be NULL.
}
void free_list(Node* head) {
while(head != NULL) { // While the list is not empty
Node* old_head = head; // Don't lose your head.
head = head -> next; // Second node becomes the new of the list.
free(old_head); // Free your mind.
}
assert(head);
}
/*
FOR VS. WHILE
for(«INIT», «CONDITION», «STEP») {
«BODY»
}
«INIT»
while(«CONDITION») {
«BODY»
«STEP»
}
*/
int main(int argc, char* argv[]) {
Node* head = NULL;
Node* tail = head;
_append(5, &head, &tail);
_append(6, &head, &tail);
_append(7, &head, &tail);
for(int i = 0; i < 15; i++) {
_append(i, &head, &tail);
}
print_list(head);
free_list(&head, &tail);
assert(head == NULL && tail == NULL); // List should be empty now.
return EXIT_SUCCESS;
}
/* vim: set tabstop=4 shiftwidth=4 fileencoding=utf-8 noexpandtab: */
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