用c语言创建一个单链表，要求创建链表能够输入元素（用键盘输入）并保持有序，插入元素（按位置插入）并保持有序，查找，删除（按位置删除）且能够删除相同的值

在C语言中，我们可以使用结构体和指针来创建一个简单的单链表，并实现添加、查找和删除功能。首先，我们需要定义一个链表节点结构：

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

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

// 创建链表
Node* createList() {
    return NULL;
}

// 添加元素到链表（按顺序）
void insert(Node** head, int value) {
    Node* newNode = (Node*)malloc(sizeof(Node));
    if (*head == NULL) {
        newNode->data = value;
        newNode->next = NULL;
        *head = newNode;
    } else if (value <= (*head)->data) {
        newNode->data = value;
        newNode->next = *head;
        *head = newNode;
    } else {
        Node* current = *head;
        while (current->next != NULL && current->next->data < value) {
            current = current->next;
        }
        newNode->data = value;
        newNode->next = current->next;
        current->next = newNode;
    }
}

// 查找元素
Node* search(Node* head, int value) {
    Node* current = head;
    while (current != NULL) {
        if (current->data == value)
            return current;
        current = current->next;
    }
    return NULL;
}

// 删除元素（按位置）
void delete(Node** head, int position) {
    if (*head == NULL || position <= 0)
        return;
    
    Node* temp = *head;
    if (position == 1) {
        *head = (*head)->next;
        free(temp);
        return;
    }

    for (int i = 1; temp != NULL && i < position - 1; i++) {
        temp = temp->next;
    }
    if (temp != NULL) {
        temp->next = temp->next->next;
        free(temp->next);
    }
}

// 打印链表
void printList(Node* head) {
    Node* current = head;
    while (current != NULL) {
        printf("%d -> ", current->data);
        current = current->next;
    }
    printf("NULL\n");
}

int main() {
    Node* head = createList();
    int choice, value, position;
    
    while (1) {
        printf("\n1. Add element\n2. Search element\n3. Delete element by position\n4. Print list\n5. Exit\n");
        scanf("%d", &choice);

        switch (choice) {
            case 1:
                printf("Enter value to add: ");
                scanf("%d", &value);
                insert(&head, value);
                break;
            case 2:
                printf("Enter value to find: ");
                scanf("%d", &value);
                Node* found = search(head, value);
                if (found)
                    printf("Found at position %d.\n", position + 1); // 位置从1开始计数
                else
                    printf("Element not found.\n");
                break;
            case 3:
                printf("Enter position to delete (1-based): ");
                scanf("%d", &position);
                delete(&head, position);
                break;
            case 4:
                printList(head);
                break;
            case 5:
                exit(0);
            default:
                printf("Invalid choice. Try again.\n");
        }
    }

    return 0;
}

这个程序实现了基本的链表操作，包括添加（add）、查找（search）、删除（delete）以及打印（print）。注意，因为是在命令行交互式环境中运行，所以没有涉及用户输入元素的结束条件。