根据输入的逆序数据采用头插法创建一个单链表，然后删除相同的数据，仅保留一个。

好的，我来解答你的问题。

首先，我们需要定义一个单链表的结构体：

typedef struct Node {
    int data;
    struct Node *next;
} Node;

然后，我们可以根据输入的逆序数据创建一个单链表：

Node *createList(int *arr, int len) {
    Node *head = NULL;
    Node *p = NULL;
    int i;
    for (i = 0; i < len; i++) {
        Node *newNode = (Node *)malloc(sizeof(Node));
        newNode->data = arr[i];
        newNode->next = head;
        head = newNode;
    }
    return head;
}

接着，我们可以遍历单链表，删除相同的数据，仅保留一个：

void removeDuplicates(Node *head) {
    Node *cur = head;
    while (cur != NULL) {
        Node *p = cur->next;
        while (p != NULL && p->data == cur->data) {
            cur->next = p->next;
            free(p);
            p = cur->next;
        }
        cur = cur->next;
    }
}

完整的代码如下：

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

typedef struct Node {
    int data;
    struct Node *next;
} Node;

Node *createList(int *arr, int len) {
    Node *head = NULL;
    Node *p = NULL;
    int i;
    for (i = 0; i < len; i++) {
        Node *newNode = (Node *)malloc(sizeof(Node));
        newNode->data = arr[i];
        newNode->next = head;
        head = newNode;
    }
    return head;
}

void removeDuplicates(Node *head) {
    Node *cur = head;
    while (cur != NULL) {
        Node *p = cur->next;
        while (p != NULL && p->data == cur->data) {
            cur->next = p->next;
            free(p);
            p = cur->next;
        }
        cur = cur->next;
    }
}

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

int main() {
    int arr[] = {1, 2, 3, 2, 4, 2, 5};
    int len = sizeof(arr) / sizeof(int);
    Node *head = createList(arr, len);
    printf("Original list: ");
    printList(head);
    removeDuplicates(head);
    printf("List after removing duplicates: ");
    printList(head);
    return 0;
}

希望能够帮助到你！