所以目前我正在尝试测试的if
函数中有一个GetNth
语句。但是当我插入一个printf
函数时,它使我注意到即使不满足条件,它也会通过if
语句,但是,当我删除printf
语句时,该程序可以正常工作。任何解释将不胜感激。
注意!这不是我的代码,我试图学习链接列表,并且正在更改尝试学习的代码!
代码:
#include <stdio.h>
#include <stdlib.h>
#include <assert.h>
/* Link list node */
struct node
{
int data;
struct node* next;
};
/* Given a reference (pointer to pointer) to the head
of a list and an int, push a new node on the front
of the list. */
void push(struct node** head_ref, int new_data)
{
/* allocate node */
struct node* new_node =
(struct node*) malloc(sizeof(struct node));
/* put in the data */
new_node->data = new_data;
/* link the old list off the new node */
new_node->next = (*head_ref);
/* move the head to point to the new node */
(*head_ref) = new_node;
}
/* Takes head pointer of the linked list and index
as arguments and return data at index*/
int GetNth(struct node* head, int index)
{
struct node* current = head;
int count = 0; /* the index of the node we're currently
looking at */
int a;
while (current != NULL)
{
if (count == index)
return(current->data);
a = current->data;
printf("\n Testing If in linked list, should bring same desired value which is 4 %d \n ",a);
count++;
current = current->next;
}
/* if we get to this line, the caller was asking
for a non-existent element so we assert fail */
assert(0);
}
/* Drier program to test above function*/
int main()
{
/* Start with the empty list */
struct node* head = NULL;
/* Use push() to construct below list
1->12->1->4->1 */
push(&head, 1);
push(&head, 4);
push(&head, 1);
push(&head, 12);
push(&head, 1);
if (head != NULL)
{
}
/* Check the count function */
printf("Element at index 3 is %d", GetNth(head, 3));
getchar();
}
最佳答案
缺少括号。
这就是为什么我是“始终添加括号”的捍卫者的原因。
编辑“解决方案”。
当前代码是:
while (current != NULL)
{
if (count == index)
return(current->data);
a = current->data;
printf("\n Testing If in linked list, should bring same desired value which is 4 %d \n ",a);
count++;
current = current->next;
}
如果不使用大括号,则if语句仅适用于下一条指令,即
return(current->data);
如果要在if块中包含多个指令,则必须创建一个带有花括号的块。
if (count == index)
{
return(current->data);
a = current->data;
printf("\n Testing If in linked list, should bring same desired value which is 4 %d \n ",a);
}
但是,您从返回指令开始,因此以下两行将永远不会执行。
重新排列说明以在退货前打印。
if (count == index)
{
a = current->data;
printf("\n Testing If in linked list, should bring same desired value which is 4 %d \n ",a);
return(current->data);
}