@@ -9,35 +9,31 @@ struct Node {
99
1010static struct Node * copyRandomList (struct Node * head )
1111{
12- if (head == NULL ) {
13- return NULL ;
14- }
15- 16- /* copy and redirect next pointer */
17- struct Node * p , * new ;
18- for (p = head ; p != NULL ; p = p -> next -> next ) {
19- new = malloc (sizeof (* new ));
20- new -> val = p -> val ;
21- new -> next = p -> next ;
22- p -> next = new ;
12+ struct Node * p , * q ;
13+ /* insert interleavingly */
14+ for (p = head ; p != NULL ; p = q -> next ) {
15+ q = malloc (sizeof (* q ));
16+ q -> val = p -> val ;
17+ q -> next = p -> next ;
18+ p -> next = q ;
2319 }
2420
2521 /* clone random pointer */
26- for (p = head ; p != NULL ; p = p -> next -> next ) {
27- new = p -> next ;
28- new -> random = p -> random != NULL ? p -> random -> next : NULL ;
22+ for (p = head ; p != NULL ; p = q -> next ) {
23+ q = p -> next ;
24+ q -> random = p -> random != NULL ? p -> random -> next : NULL ;
2925 }
3026
3127 struct Node dummy ;
3228 struct Node * prev = & dummy ;
33- for (p = head ; p != NULL ; p = p -> next ) {
34- new = p -> next ;
35- p -> next = new -> next ;
36- /* correct the actual next pointer of the new list */
37- prev -> next = new ;
38- prev = new ;
39- new -> next = NULL ;
29+ prev -> next = head ;
30+ for (p = head ; p != NULL ; p = q -> next ) {
31+ q = p -> next ;
32+ /* separate q list */
33+ prev -> next = q ;
34+ prev = q ;
4035 }
36+ /* q->next = NULL */
4137
4238 return dummy .next ;
4339}
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