Created
March 30, 2010 21:43
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/** see http://stackoverflow.com/questions/2242553/copy-a-linked-list/2242645#2242645 */ | |
#include <assert.h> | |
#include <stdio.h> | |
#include <stdlib.h> // malloc | |
typedef struct Node* pNode; | |
typedef void (*node_visitor_t)(pNode); | |
struct Node { | |
int data; | |
pNode next; | |
pNode other; | |
}; | |
static pNode newnode(pNode head, int data) { | |
pNode node = (pNode)malloc(sizeof(*node)); | |
if (!node) { | |
perror("malloc"); | |
exit(1); | |
} | |
node->next = head; | |
node->data = data; | |
node->other = NULL; | |
return node; | |
} | |
static void push_front(pNode* phead, int data) { | |
assert(phead); | |
*phead = newnode(*phead, data); | |
} | |
static void visit(pNode head, node_visitor_t visitor) { | |
while (head) { | |
pNode t = head->next; | |
visitor(head); | |
head = t; | |
} | |
} | |
static void destroy(pNode head) { | |
visit(head, (node_visitor_t)free); | |
} | |
static void print_node(pNode node) { | |
printf("%d ", node->data); | |
} | |
static pNode copy_list(pNode head) { | |
// pre-condition: node->other either points into the list or NULL | |
if (!head) return NULL; | |
// | |
pNode node = head, copied = NULL, cnode = NULL; | |
for ( ; node; node = node->next->next) { | |
// make copy | |
cnode = newnode(node->next, node->data); | |
cnode->other = node->other; | |
if (node == head) | |
copied = cnode; | |
// insert the copy between originals | |
node->next = cnode; | |
// node -> cnode -> (orig)node->next | |
} | |
// | |
for (node = head; node && node->next; | |
node = node->next->next /* only original nodes */) | |
if (node->other) | |
node->next->other = node->other->next; | |
else | |
node->next->other = NULL; | |
// restore lists | |
node = head; cnode = copied; | |
for (;cnode && cnode->next; node = node->next, cnode = cnode->next) { | |
node->next = node->next->next; | |
cnode->next = cnode->next->next; | |
} | |
node->next = NULL; | |
return copied; | |
} | |
int main(void) { | |
pNode head = NULL; | |
// init the list | |
size_t i = 10; | |
while(i-->0) | |
push_front(&head, i); | |
// assign arbitrary other nodes | |
head->other = head; | |
head->next->other = head; | |
head->next->next->other = NULL; | |
head->next->next->next->other = head->next->next->next->next->next->next; | |
visit(head, print_node); | |
puts("\n"); | |
pNode copied = copy_list(head); | |
visit(copied, print_node); | |
puts("\n"); | |
visit(head, print_node); | |
puts("\n"); | |
// check links | |
assert(head->other == head); | |
assert(head->next->other == head); | |
assert(head->next->next->other == NULL); | |
assert(head->next->next->next->other == head->next->next->next->next->next->next); | |
assert(copied->other == copied); | |
assert(copied->next->other == copied); | |
assert(copied->next->next->other == NULL); | |
assert(copied->next->next->next->other == copied->next->next->next->next->next->next); | |
pNode node = head, cnode = copied; | |
for ( ; node; node=node->next, cnode=cnode->next) { | |
assert(node->data == cnode->data); | |
assert(node->next != cnode->next || node->next == NULL); | |
assert(node->other != cnode->other || node->other == NULL); | |
} | |
destroy(copied); | |
destroy(head); | |
return 0; | |
} |
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