[英]How do I swap the nodes of a linked list in a bubble-sort algorithm?
在 C 中,我必須編寫一個冒泡排序 function 來交換節點而不是 LinkedList 的值,但我無法完成它。 這是代碼(如您所見,順序不正確):
#include <stdio.h>
#include <malloc.h> // malloc, free
#include <stddef.h> // NULL
// defining 'int' as data_t
typedef int data_t;
typedef struct node_s {
data_t data;
struct node_s* next;
} node_t;
node_t** list_new() {
node_t** list = malloc(sizeof **list);
if (!list) return NULL;
*list = NULL;
return list;
}
void list_delete(node_t** list) {
node_t *node, *next;
for (node = *list; node; node = next) {
next = node->next;
free(node);
}
}
node_t* list_push_front(node_t** list, data_t data) {
node_t* node = malloc(sizeof(node_t));
if (!node) return NULL;
node->data = data;
node->next = *list;
return *list = node;
}
// IS EASY TO SWAP THE VALUES
/*
void swap(data_t* a, data_t* b) {
data_t c = *a;
*a = *b;
*b = c;
}
void simple_bubble_sort(node_t** list) {
for(node_t* i = *list; i; i = i->next)
for(node_t* j = *list; j->next; j = j->next)
if(j->data > j->next->data)
swap(&(j->data), &(j->next->data));
}
*/
// MUCH LESS EASY TO SWAP THE NODES
void swap_node(node_t** prev_node_A, node_t** node_A, node_t** node_B) {
node_t *last_node = (*node_B)->next;
node_t *first_node = *node_A;
node_t *second_node = *node_B;
if (prev_node_A) {
(*prev_node_A)->next = second_node;
(*prev_node_A)->next->next = first_node;
(*prev_node_A)->next->next->next = last_node;
} else {
(*node_A) = second_node;
(*node_A)->next = first_node;
(*node_A)->next->next = last_node;
}
}
void simple_bubble_sort(node_t** list) {
for(node_t* i = *list; i->next; i = i->next)
for (node_t *j = *list; j->next->next; j = j->next) {
if (j == *list) {
if (j->data > j->next->data) {
*list = j->next;
swap_node(NULL, &j, &(j->next));
}
}
else {
if (j->next->data > j->next->next->data)
swap_node(&j, &(j->next), &(j->next->next));
}
//printf("%i,%i | %i, %i, %i, %i \n", i->data, j->data, (*list)->data, (*list)->next->data, (*list)->next->next->data, (*list)->next->next->next->data);
//system("pause");
}
}
int main() {
// Create List
node_t** list = list_new();
if (!list)
goto memory_allocation_failure;
// Add values to List
for(int i=0; i<10; i++)
if (!list_push_front(list, i))
goto memory_allocation_failure;
// Print List
for (node_t* node = *list; node != NULL; node = node->next)
printf("%i\n", node->data);
// Swap Test
//swap_node(NULL, &(*list), &((*list)->next));
//swap_node(&(*list), &((*list)->next), &((*list)->next->next));
// Sort List
printf("-- Bubble Sort --\n");
simple_bubble_sort(list);
// Print List
for (node_t* node = *list; node != NULL; node = node->next)
printf("%i\n", node->data);
// Delete List
list_delete(list);
return 0;
// Error Handler
memory_allocation_failure:
printf("Memory Allocation Failure");
return 1;
}
這是 function swap
。
void swap( node_t **current )
{
node_t *tmp = ( *current )->next->next;
( *current )->next->next = *current;
*current = ( *current )->next;
( *current )->next->next = tmp;
}
這是 function simple_bubble_sort
void simple_bubble_sort( node_t **head )
{
if ( *head )
{
for ( node_t **first = head, *sorted = NULL, *last = sorted;
( *first )->next != last;
last = sorted )
{
sorted = ( *first )->next;
for ( node_t **current = first; ( *current )->next != last; current = &( *current )->next )
{
if ( ( *current )->next->data < ( *current )->data )
{
swap( current );
sorted = ( *current )->next;
}
}
}
}
}
調查他們。
注意 header <malloc.h>
不是標准的 C header。 而是使用 header <stdlib.h>
。
您需要修改當前代碼。 例如這個 function
node_t** list_new() {
node_t** list = malloc(sizeof **list);
if (!list) return NULL;
*list = NULL;
return list;
}
沒有意義它應該被刪除。
您需要的只是在 main 中定義一個指針,例如
node_t *head = NULL;
並將其傳遞給函數,例如 function simple_bubble_sort
simple_bubble_sort( &head );
或者 function list_push_front
應該定義為
int list_push_front(node_t** list, data_t data)
{
node_t* node = malloc(sizeof(node_t));
int success = node != NULL;
if ( success )
{
node->data = data;
node->next = *list;
*list = node;
}
return success;;
}
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