实现
我正在编写一个程序来删除大于x的节点。我想在删除后返回链表的根节点。我将新的根节点保存在变量"中；根"；。但不幸的是，当我在main函数中获得root时，值似乎是0。有人能帮我确定问题吗？**
// structure of a node
struct Node {
int data;
Node* next;
};
// function to get a new node
Node* getNode(int data)
{
Node* newNode = (Node*)malloc(sizeof(struct Node));
newNode->data = data;
newNode->next = NULL;
return newNode;
}
// function to delete all the nodes from the list
// that are greater than the specified value x
Node *deleteGreaterNodes(Node* head_ref, int x)
{
Node *temp = head_ref, *prev;
static Node *root;
// If head node itself holds the value greater than 'x'
if (temp != NULL && temp->data > x) {
head_ref = temp->next; // Changed head
free(temp); // free old head
temp = head_ref; // Change temp
}
root = temp;
// Delete occurrences other than head
while (temp != NULL) {
// Search for the node to be deleted,
// keep track of the previous node as we
// need to change 'prev->next'
while (temp != NULL && temp->data <= x) {
prev = temp;
temp = temp->next;
}
// If required value node was not present
// in linked list
if (temp == NULL)
return 0;
// Unlink the node from linked list
prev->next = temp->next;
free (temp); // Free memory
// Update Temp for next iteration of
// outer loop
temp = prev->next;
}
return head_ref;
}
// function to a print a linked list
void printList(Node* head)
{
while (head) {
printf("%d ",head->data);
head = head->next;
}
}
// Driver program to test above
int main()
{
static Node *root;
// Create list: 7->3->4->8->5->1
Node* head = getNode(7);
head->next = getNode(3);
head->next->next = getNode(4);
head->next->next->next = getNode(8);
head->next->next->next->next = getNode(5);
head->next->next->next->next->next = getNode(1);
int x = 3;
printf("Original List: ");
printList(head);
root = deleteGreaterNodes(head, x);
printf("nModified List: ");
printList(root);
return 0;
}
deleteGreaterNodes的一种简单方法是使用额外级别的间接访问Node *链接。
// function to delete all the nodes from the list
// that are greater than the specified value x
Node *deleteGreaterNodes(Node* head_ref, int x)
{
Node **link = &head_ref; // Point to the pointer to the first node.
Node *cur;
while ((cur = *link) != NULL) {
if (cur->data > x) {
// The current node needs to be deleted from the list.
// Change the link pointing to the current node to point to the next node.
*link = cur->next;
// Delete the current node.
free(cur);
} else {
// The current node is to be kept on the list.
// Get a pointer to the link to the next node.
link = &cur->next;
}
}
return head_ref;
}
对于初学者来说，不要在一个翻译单元中混合使用两种语言C和C++。
编写一个C或C++程序。
例如，C 中的声明
// structure of a node
struct Node {
int data;
Node* next;
};
是不正确的，你必须写
// structure of a node
struct Node {
int data;
struct Node* next;
};
声明静态变量root没有什么意义
static Node *root;
然后再加一个变量CCD_ 4。
// Create list: 7->3->4->8->5->1
Node* head = getNode(7);
你的函数deleteGreaterNodes太复杂了，和任何复杂的函数一样，它在这个代码片段中包含一个错误
// If required value node was not present
// in linked list
if (temp == NULL)
return 0;
因为它返回空指针而不是返回指针CCD_ 6。
这是根据C语言调整的更新程序，其中包含修改后的函数deleteGreaterNodes。
#include <stdio.h>
#include <stdlib.h>
// structure of a node
struct Node {
int data;
struct Node* next;
};
// function to get a new node
struct Node* getNode(int data)
{
struct Node* newNode = ( struct Node * )malloc(sizeof(struct Node));
newNode->data = data;
newNode->next = NULL;
return newNode;
}
// function to delete all the nodes from the list
// that are greater than the specified value x
struct Node *deleteGreaterNodes( struct Node* head_ref, int x )
{
while ( head_ref && x < head_ref->data )
{
struct Node *tmp = head_ref;
head_ref = head_ref->next;
free( tmp );
}
if ( head_ref )
{
for ( struct Node *current = head_ref; current->next != NULL; )
{
if ( x < current->next->data )
{
struct Node *tmp = current->next;
current->next = current->next->next;
free( tmp );
}
else
{
current = current->next;
}
}
}
return head_ref;
}
// function to a print a linked list
void printList(struct Node* head)
{
while (head) {
printf("%d ",head->data);
head = head->next;
}
}
// Driver program to test above
int main()
{
struct Node* head = getNode(7);
head->next = getNode(3);
head->next->next = getNode(4);
head->next->next->next = getNode(8);
head->next->next->next->next = getNode(5);
head->next->next->next->next->next = getNode(1);
int x = 3;
printf( "Original List: " );
// printf("Original List: ");
printList(head);
head = deleteGreaterNodes(head, x);
printf("nModified List: ");
printList( head );
return 0;
}
程序输出为
Original List: 7 3 4 8 5 1
Modified List: 3 1