两个简单的链表操作

谈起链表，还是原来在学校里上《数据结构》的时候，自己动手写了一套完整的代码，现在想起来都不知道丢哪里去了。不过那个时候写的东西都是些基本的链表操作，昨天偶然碰到了两个新鲜一点的：一个是将链表反向，另外一个稍微难点，合并两个已经排好序的链表，当然要求合并后的链表仍然有序呀！

下面给出链表的基本数据结构：

 

struct Node { int data; Node * next;};

另外再加一个添加节点的操作，这样方便验证接下来要实现的功能。

添加节点：

void AddNode(Node ** head , int data){ Node * pTemp; Node * pNode = (Node*)malloc(sizeof(Node)); pNode->data = data; pNode->next = NULL; if (*head == NULL) { *head = pNode; } else { pTemp = *head; while (pTemp->next) { pTemp = pTemp->next; } pTemp->next = pNode; }}

显示整个链表：

void Display(Node * head){ while (head) { printf("%2d " , head->data); head = head->next; } printf("/n");}

销毁整个链表：

 

void Destroy(Node * head){ Node * pNode; while (head) { pNode = head->next; free(head); head = pNode; }}

第一个操作是链表的反向，这个比较简单：

void Reverse(Node ** head){ unsigned char sign; Node * pHead , * pNext , * pTemp; pHead = *head; if (pHead == NULL) { return; } sign = 1; pNext = pHead->next; while (pNext) { pTemp = pNext->next; pNext->next = pHead; if (sign == 1) { pHead->next = NULL; sign = 0; } pHead = pNext; pNext = pTemp; } *head = pHead;}

第二个是合并已经排好序的链表，我用了两种方法来实现这个功能，递归和普通的方式：

递归实现如下：

void JoinRecusive(Node * head1 , Node * head2 , Node ** pResult){ Node * pNode = *pResult; if (head1 != NULL && head2 == NULL) { if (pNode == NULL) { *pResult = head1; pNode = head1; } else { pNode->next = head1; } return; } if (head1 == NULL && head2 != NULL) { if (pNode == NULL) { *pResult = head2; pNode = head2; } else { pNode->next = head2; } return; } if (head1 != NULL && head2 != NULL) { if(head1->data <= head2->data) { if (pNode == NULL) { *pResult = head1; pNode = head2; } else { pNode->next = head1; pNode = pNode->next; } head1 = head1->next; JoinRecusive(head1 , head2 , &pNode); } else { if (pNode == NULL) { *pResult = head2; pNode = head2; } else { pNode->next = head2; pNode = pNode->next; } head2 = head2->next; JoinRecusive(head1 , head2 , &pNode); } }}

非递归实现如下：

Node * Join(Node * head1 , Node * head2){ Node * pNode , *pHead; pNode = pHead = NULL; while(head1 != NULL && head2 != NULL) { if(head1->data <= head2->data) { if (pNode == NULL) { pHead = pNode = head1; } else { pNode->next = head1; pNode = pNode->next; } head1 = head1->next; } else { if (pNode == NULL) { pHead = pNode = head2; } else { pNode->next = head2; pNode = pNode->next; } head2 = head2->next; } } if (head1 != NULL) { pNode->next = head1; } if (head2 != NULL) { pNode->next = head2; } return pHead;}

下面是一段简单的测试程序：

 Node * head1 = NULL;Node * head2 = NULL;Node * head3 = NULL;void main(){ AddNode(&head1 , 10); AddNode(&head1 , 11); AddNode(&head1 , 12); AddNode(&head1 , 13); AddNode(&head1 , 14); AddNode(&head1 , 15); AddNode(&head1 , 16); AddNode(&head1 , 17); AddNode(&head2 , 1); AddNode(&head2 , 2); AddNode(&head2 , 3); AddNode(&head2 , 22); AddNode(&head2 , 25); AddNode(&head2 , 26); AddNode(&head2 , 27); Display(head1); Display(head2); //head3 = Join(head1 , head2); JoinRecusive(head1 , head2 , &head3); Display(head3);}