你的函数实现是错误的。
甚至第一个 while 循环中的条件
while (ptr1 != NULL && ptr1->next != NULL)
是不正确的,因为如果列表仅包含一个节点,则不会执行循环并且函数将返回 0。
并在函数内变量counter
没有被改变。
这是一个演示程序,展示了该功能如何Find_cardinal
最好这样命名count_distinct
可以实施。
#include <stdio.h>
#include <stdlib.h>
struct Node
{
int data;
struct Node *next;
};
typedef struct Node Node_t;
size_t assign( Node_t **head, const int a[], size_t n )
{
while ( *head )
{
Node_t *tmp = *head;
head = &( *head )->next;
free( tmp );
}
size_t i = 0;
for ( ; i < n && ( *head = malloc( sizeof( Node_t ) ) ) != NULL; i++ )
{
( *head )->data = a[i];
( *head )->next = NULL;
head = &( *head )->next;
}
return i;
}
size_t count_distinct( const Node_t *head )
{
size_t n = 0;
for ( const Node_t *current = head; current != NULL; current = current->next )
{
const Node_t *prev = head;
while ( prev != current && prev->data != current->data )
{
prev = prev->next;
}
if ( prev == current ) ++n;
}
return n;
}
FILE * display( const Node_t *head, FILE *fp )
{
for ( ; head != NULL; head = head->next )
{
fprintf( fp, "%d -> ", head->data );
}
fputs( "null", fp );
return fp;
}
int main(void)
{
Node_t *head = NULL;
int a[] = { 1, 2, 1, 1, 3, 4 };
assign( &head, a, sizeof( a ) / sizeof( *a ) );
fputc( '\n', display( head, stdout ) );
printf( "There are %zu distinct data in the list.\n", count_distinct( head ) );
return 0;
}
程序输出是
1 -> 2 -> 1 -> 1 -> 3 -> 4 -> null
There are 4 distinct data in the list.