c - 将不同的单词保存到链接列表中

Question

基本上我这里有2个链表:list和distinct。有几组单词之前已保存到“列表”结构中。我要编写一个程序，它会找到不同/唯一的单词并将其保存到“不同”结构中。这是我到目前为止根据我的指针概念得到的结果。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:(如果您需要对代码进行额外注释，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，您检查 ori 和 copy 是否为 NULL，然后您立即取消引用这些 NULL 指针!