Question

我正致力于实现双向链表。我希望链表受到一定程度的限制。当列表变长时，删除最后一个节点。我在这里有一些问题。我想定义尾部，以便我不必搜索结束。这是我正在处理它的实现将允许长度为4然后开始删除最后一个节点。

/* Doubly Linked List implementation */
#include<stdio.h>
#include<stdlib.h>
#include<string.h>

struct Node  {
    char command[1024];
    struct Node* next;
    struct Node* prev;
};

struct Node* head; //global pointing to head
struct Node* tail; //global pointing to tail

//Creates a new Node and returns pointer to it. 
struct Node* GetNewNode(char *line) {
    struct Node* newCommand = (struct Node*)malloc(sizeof(struct Node));
        int i = 0;
        while(line[i] != '\0'){
            newCommand->command[i] = line[i];
            i++;
        }
        newCommand->prev = NULL;
    newCommand->next = NULL;
    return newCommand;
}

//Inserts a Node at head of doubly linked list
void InsertAtHead(char *line) {
    struct Node* newCommand = GetNewNode(line);
    if(head == NULL) {
        head = newCommand;
        tail = newCommand;
        return;
    }
    head->prev = newCommand;
    newCommand->next = head; 
    head = newCommand;
}
//Use tail to delete the last node
void deleteLast(){
    struct Node* temp = tail;
    tail = temp->prev;
    free(tail->next);
    tail->next = NULL;
}
//Print in reverse orer
void Print() {
    struct Node* temp = tail;
    while(temp != NULL) {
        printf("%s \n",temp->command);
        temp = temp->prev;
    }
}

int main() {

        int numNodes = 0;
        char line[1024];
        head = NULL; 
        tail = NULL; // empty list. set head/tail as NULL. 
        printf("next node: ");
        while (fgets(line, 1024, stdin)) {
            line[strlen(line)-1] = '\0';
            if(numNodes == 4){
                numNodes -= 1;
                deleteLast();
            }
            InsertAtHead(line);Print();
            numNodes += 1;
            printf("next node: ");
        }
        Print();
}

似乎是删除了最后一个节点，但之后打印了一些奇怪的符号。我猜它是一个问题我如何免费（）但我无法弄明白。请注意，此代码中的一部分来自https://gist.github.com/mycodeschool/7429492

Answer 1

您的代码看起来很好，但是，将命令复制到节点时出错：

    while(line[i] != '\0'){
        newCommand->command[i] = line[i];
        i++;
    }

应该是：

    while(line[i] != '\0'){
        newCommand->command[i] = line[i];
        i++;
    }
    newCommand->command[i] = '\0';

（您忘记终止复制的命令。）

另请注意，您必须检查是否超出可用空间，例如：

    while(i<1023 && line[i] != '\0'){
        newCommand->command[i] = line[i];
        i++;
    }
    newCommand->command[i] = '\0';

双向链表删除最后一个C.

1 个答案: