Question

基本上我在这里有2个链表：list和distinct。有一些单词已经保存在“list”结构中。是否会写一个程序，它会找到不同/独特的单词并将其保存到'distinct'结构中。这是我到目前为止根据指针的概念得到的。然而，当我尝试打印'distinct'时，程序崩溃了:(如果我错了，请纠正我。

struct list {
char string[50];
struct list *next;
};

struct distinct {
char string[50];
struct distinct *next; 
};

void checkdistinct() { 

 list *ori = NULL;
 distinct *copy = NULL;
 distinct *check = NULL;

if(ori == NULL && copy == NULL) { //first time.
    ori = ori->next;
    copy = copy->next;
    copy = (distinct*)malloc(sizeof(distinct));
    strcpy(copy->string, ori->string);
    ori = ori->next;
    copy = copy->next;
}
else {}

while(ori!=NULL) {
    check = check->next;

   while(check != NULL) {
    if(strcmp(ori->string, check->string)!=0) {
        check = check->next;
    }
    else {
        ori = ori->next;
        check = NULL;
    }

 }

    //only compare same casing words, for now.
    copy = (distinct*)malloc(sizeof(distinct));
    strcpy(copy->string, ori->string);
    ori = ori->next;
    copy = copy->next;      
 }
}

当我尝试在main中打印时，它会崩溃:(如果您需要额外的代码注释，请回复。谢谢！

Answer 1

这三行可能是罪魁祸首：

if(ori == NULL && copy == NULL) { //first time.
    ori = ori->next;
    copy = copy->next;

在这里检查ori和copy是NULL，然后立即取消引用这些NULL指针！

Answer 2

在您的代码中，distinct不是变量的名称，而是结构的名称。你似乎误解了指针，希望这会有所帮助，尽管它与你的问题没有直接关系。

我遗漏了很多错误检查，以使代码看起来更简单。

typedef struct listnode {
    char string[50];
    struct listnode *next;
} list_node;

typedef struct listbase {
    list_node *head;
    int numberOfElements;
} list;

/* Add a new string at the start of the list
*/
void ListPrepend(list *myList, char *myString) {
    list_node *newNode = malloc(sizeof *newNode); /* create node to store string */

    strcpy(newNode->string, myString); /* copy string into node */
    newNode->next = myList->head;      /* New node now followed by whole list */
    myList->head = newNode;            /* List now starts with new node */
    myList->numberOfElements++;
}

/* Add a new string at the end of the list
*/
void ListAppend(list *myList, char *myString) {
    list_node *newNode = malloc(sizeof *newNode), /* create node to store string */
              *currentNode = myList->head; /* pointer to node so we can find the end */

    strcpy(newNode->string, myString); /* copy string into new node */
    newNode->next = NULL;              /* Nothing following this node */

    if ( myList->head == NULL ) {
        myList->head = newNode; /* we didn't have a start node so assign it */
    } else {
        /* if there is a next node, move to it */
        while ( currentNode->next != NULL ) {
            currentNode = currentNode->next;
        }
        /* there is no next node so add new node on the end */
        currentNode->next = newNode;
    }
    myList->numberOfElements++;
}

/* Show the list in order head to tail
*/
void ListDisplay(list *myList) {
    list_node *currentNode = myList->head;

    while ( currentNode != NULL ) {
        printf("%s\n", currentNode->string);
        currentNode = currentNode->next;
    }
}

int main() {
    list distinct = {0}; /* Now there is a variable called distinct */
    char name[][20] = {"Lim Zheng Yue", "Monkey", "Dave"};

    ListAppend(&distinct, name[0]);
    ListAppend(&distinct, name[1]);
    ListPrepend(&distinct, name[2]);
    ListDisplay(&distinct);
}

将不同的单词保存到链表中

2 个答案: