用c语言创建链表，编写程序实现在指定位置插入，删除，修改节点，并返回原来节点的值

好的，下面是一个用 C 语言创建链表并实现插入、删除和修改节点的示例程序：

#include <stdio.h>
#include <stdlib.h>

// 定义链表节点结构体
typedef struct Node {
    int data;
    struct Node* next;
} Node;

// 创建链表
Node* createList() {
    Node* head = NULL;  // 头节点
    Node* tail = NULL;  // 尾节点

    int num;
    printf("输入链表节点的值（输入-1结束）：\n");
    while (1) {
        scanf("%d", &num);

        if (num == -1) {
            break;
        }

        Node* newNode = (Node*)malloc(sizeof(Node));
        newNode->data = num;
        newNode->next = NULL;

        if (head == NULL) {
            head = newNode;
            tail = newNode;
        } else {
            tail->next = newNode;
            tail = newNode;
        }
    }

    return head;
}

// 在指定位置插入节点
void insertNode(Node** head, int position, int value) {
    Node* newNode = (Node*)malloc(sizeof(Node));
    newNode->data = value;

    if (position == 0) {
        newNode->next = *head;
        *head = newNode;
    } else {
        Node* current = *head;
        int i = 0;

        while (i < position - 1 && current != NULL) {
            current = current->next;
            i++;
        }

        if (current != NULL) {
            newNode->next = current->next;
            current->next = newNode;
        } else {
            printf("插入位置无效！\n");
            free(newNode);
        }
    }
}

// 删除指定位置的节点
void deleteNode(Node** head, int position) {
    if (*head == NULL) {
        printf("链表为空，无法删除节点！\n");
        return;
    }

    Node* temp = *head;

    if (position == 0) {
        *head = (*head)->next;
        free(temp);
    } else {
        Node* current = *head;
        int i = 0;

        while (i < position - 1 && current != NULL) {
            current = current->next;
            i++;
        }

        if (current != NULL && current->next != NULL) {
            temp = current->next;
            current->next = temp->next;
            free(temp);
        } else {
            printf("删除位置无效！\n");
        }
    }
}

// 修改指定位置的节点值
void modifyNode(Node* head, int position, int value) {
    Node* current = head;
    int i = 0;

    while (i < position && current != NULL) {
        current = current->next;
        i++;
    }

    if (current != NULL) {
        current->data = value;
    } else {
        printf("修改位置无效！\n");
    }
}

// 打印链表
void printList(Node* head) {
    printf("链表的值为：");

    while (head != NULL) {
        printf("%d ", head->data);
        head = head->next;
    }

    printf("\n");
}

// 主函数
int main() {
    Node* head = createList();
    printList(head);

    int position, value;

    printf("输入要插入的位置和值：\n");
    scanf("%d %d", &position, &value);
    insertNode(&head, position, value);
    printList(head);

    printf("输入要删除的位置：\n");
    scanf("%d", &position);
    deleteNode(&head, position);
    printList(head);

    printf("输入要修改的位置和值：\n");
    scanf("%d %d", &position, &value);
    modifyNode(head, position, value);
    printList(head);

    return 0;
}

这个程序首先会创建一个链表，然后根据用户的输入执行插入、删除和修改节点的操作，并打印每次操作后链表的值。请根据自己的需要进行修改和扩展。希望对你有帮助！