在C中删除链接列表
下面我创建一个链接列表,然后试图删除它,但程序将编译并运行,但链接列表不会删除,并且程序陷入循环或某物(基本上它不会终止,因为我不得不手动终止它)在C中删除链接列表
任何人都可以建议我去哪里错了,在写'deletePoly'函数之前一切都很好(即程序会编译并运行)没问题,但我已经通过鳕鱼100次,我似乎无法看到问题是什么。
这里是我的代码:
#include <stdlib.h>
#include <stdio.h>
#include <time.h>
#define MEMORY_SIZE (15)
typedef struct link {
double coeff;
int pow;
struct link * next;
} poly;
poly *polyArray[MEMORY_SIZE];// array of 15 polynomials to play with
// /** The function prototypes */
void createPoly(poly **);
void showPoly(poly *);
void deletePoly(poly *);
int main(void) {
int a;
for(a = 0; a < MEMORY_SIZE; a++)
{
polyArray[a] = NULL;//Initialise each element of the array of pointers to NULL
}//end for
createPoly(&polyArray[0]);
showPoly(polyArray[0]);
srand(time(NULL));
createPoly(&polyArray[1]);
showPoly(polyArray[1]);
showPoly(polyArray[0]);
int count;
for(count = 0; count < MEMORY_SIZE; count++)
{
deletePoly(polyArray[count]);
}
showPoly(polyArray[0]);
return 0;
}// End Main Function
//////////////////////////////////////////////////////////////////////////////////////
void createPoly(poly **node) {
poly *tempnode; //To hold the temporary last address
tempnode = (poly*)malloc(sizeof(poly)); //create the first node
*node = tempnode; //Store the head address to the reference variable
int flag = 1 + rand()%3;; // A flag to control the number of terms
int counter;
for(counter = 0; counter <= flag; counter++)
{
tempnode->pow = (flag-counter);
tempnode->coeff = ((double)(rand()%20))/((double)(1 + rand()%20));
if((counter < flag) && (counter >= 0) )
{
tempnode->next = (poly*)malloc(sizeof(poly)); //Grow the list
}
else if (counter == flag)
{
tempnode->next = NULL;
}
tempnode = tempnode->next;
}
}//end function createPoly
void deletePoly(poly *node) {
poly *temp;//Create pointer to poly called 'temp'
while(node->next != NULL);
{
temp = node->next;//Assign the address of the next node to 'temp'
free(node);//Delete the current node
node = temp;//Assign the address of the next node in the list to 'node'
}//end while
node = NULL;//Set pointer 'node' to NULL to prevent a "lingering" pointer
}//end function 'deletePoly'
void showPoly(poly * node) {
while(node->next != NULL) {
if(node->coeff == 0)
{
node = node->next;
}
else if(node->coeff == 1 && node->pow > 1)
{
printf("[x^%i]", node->pow);
node = node->next;
}
else if(node->coeff == 1 && node->pow == 1)
{
printf("[x]");
node = node->next;
}
else if(node->coeff != 0 && node->pow == 0)
{
printf("(%.2lf)", node->coeff);
node = node->next;
}
else if(node->pow == 0 && node->coeff == 0)
{
node = node->next;
}
else if(node->coeff != 1 && node->pow > 1 && node->coeff != 0)
{
printf("(%.2lf)[x^%i]", node->coeff, node->pow);
node = node->next;
}
else if(node->coeff != 1 && node->pow == 1 && node->coeff != 0)
{
printf("(%.2lf)[x]", node->coeff);// no need to print x to the power 0
node = node->next;
}
if(node->next != NULL)
{
printf(" + ");
}
}
}//end function showPoly
您删除代码应该是:
void deletePoly(poly* node)
{
poly* next;
while (node != NULL)
{
next = node->next;
free(node);
node = next;
}
}
当我使用typedef将该类型的名称更改为poly时,为什么我必须写结构节点? – SlamDunkMonk 2014-11-22 16:59:58
@ user4225083是的,一旦你被警告,你可以使用poly。我只是在这里通用 – Gopi 2014-11-22 17:01:50
好的,谢谢。你有(node!= NULL)这是为什么?我对自己的方式的理解是,我正在访问名为next的每个节点的成员,并且看看它是否指向另一个节点,显然这不起作用。我对你的方式的理解是,在while body的第一行中,接下来将下一个节点的地址分配给指针变量,然后释放当前节点并将指针指向下一个节点(即next)现在延时指针变量'节点',当然,如果这个值为空,while循环将结束。它是否正确? – SlamDunkMonk 2014-11-22 17:22:55
'而(!节点 - >未来= NULL);' - >'而(节点= NULL)'和'node = NULL'不起作用。 – BLUEPIXY 2014-11-22 15:41:25