【练习】P62

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/*---分别对单链表和双链表，只使用指针来交换两个相邻的元素。---*/

/*-单链表版本-*/#include <stdio.h>#include <stdlib.h>struct Node{int val;struct Node *next;};Node *findEnd(Node *list){while(list->next) list = list->next;return list;}void insert(int val, Node *list){Node *p = (Node *)malloc(sizeof(Node));p->val = val; p->next = NULL;Node *end = findEnd(list);end->next = p;}Node *creatNewList(){return (Node *)malloc(sizeof(Node));}void deleteList(Node *list){Node *p;while(list){p = list->next;free(list);list = p;}}void print(Node *list, int k){int i = 0;while(i < k){list = list->next;++i;if(list == NULL){printf("Out of list length!");return;}}printf("%d ", list->val);}Node *find(int k, Node *list){int i = 0;while(i < k){list = list->next;++i;if(list == NULL){printf("Out of list length!");return NULL;}}return list;}void swap(int a, int b, Node *list){Node *k = find(a - 1, list);Node *p1 = k->next;Node *p2 = p1->next;k->next = p2;p1->next = p2->next;p2->next = p1;}int main(){Node *L = creatNewList(), *ptr;Node *P = creatNewList();L->next = NULL;int a;while(scanf("%d", &a) == 1)insert(a, L);swap(3, 4, L);ptr = L->next;while(ptr){printf("%d ", ptr->val);ptr = ptr->next;}printf("\n");deleteList(L);return 0;}

/*-双链表版本-*/#include <stdio.h>#include <stdlib.h>/*表结点类型*/struct Node{int val;Node *pre, *next;};/*创建一个表头即空双链表*/Node *creatList(){return (Node *)malloc(sizeof(Node));}/*在链表尾端插入元素*/void insert(int val, Node *list){Node *p = list;while(p->next) p = p->next;p->next = (Node *)malloc(sizeof(Node));p->next->val = val;p->next->next = NULL;p->next->pre = p;}/*找到第i个元素的位置*/Node *find(int i, Node *list){while(i--){list = list->next;if(list == NULL){printf("Out of list length!\n");return NULL;}}return list;}/*交换两个相邻元素,先改中间的指针*/void swap(int i, int j, Node *list){Node *p1 = find(i, list);Node *p2 = p1->next;p2->pre = p1->pre;p1->next = p2->next;p1->pre = p2;p2->next = p1;p2->pre->next = p2;p1->next->pre = p1;}/*销毁链表*/void deleteList(Node *list){Node *p;while(list){p = list;list = list->next;free(p);}}int main(){Node *list = creatList();list->next = NULL; list->pre = NULL;int a;while(scanf("%d", &a) == 1)insert(a, list);swap(3, 4, list);Node *ptr = list->next;while(ptr){printf("%d ", ptr->val);ptr = ptr->next;}deleteList(list);return 0;}

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