关于#链表#的问题，如何解决？

调了一天程序了，题目是将两个链表合并病按照学号升降排序，不知道是哪里出了问题

实现的是2个有序链表按升序排，修改了合并处的代码

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

struct circle{
    int ID;
    char name;
    struct circle* next;
};

int main() {
    struct circle* head = (struct circle*) malloc(sizeof(struct circle));
    head->next=NULL;
    struct circle* p;
    p = head;
    int n;
    printf("请输入表长：");
    scanf("%d", &n);
    for (int i = 1; i <= n; i++) {
        struct circle* s = (struct circle*) malloc(sizeof(struct circle));
        p->next = s;
        printf("请输入ID: ");
        scanf("%d", &(s->ID));
        printf("请输入name: ");
        getchar();
        scanf("%c", &(s->name));
        s->next = NULL;
        p = s;
    }
    p = head;

    struct circle* head1 = (struct circle*) malloc(sizeof(struct circle));
    head1->next=NULL;
    struct circle* p1;
    p1 = head1;
    int k;
    printf("请输入表长：");
    scanf("%d", &k);
    for (int i = 1; i <= k; i++) {
        struct circle* s = (struct circle*) malloc(sizeof(struct circle));
        p1->next = s;
        printf("请输入ID: ");
        scanf("%d", &(s->ID));
        printf("请输入name: ");
        getchar();
        scanf("%c", &(s->name));
        s->next = NULL;
        p1 = s;
    }
    p1 = head1;

    struct circle* head2 = (struct circle*) malloc(sizeof(struct circle));
    head2->next=NULL;
    struct circle* p2;
    p2 = head2;
    p = p->next;
    p1 = p1->next;

    while(p != NULL || p1 != NULL) {
        if (p1 == NULL || (p != NULL && p->ID < p1->ID)) {
            p2->next = p;
            p2 = p;
            p = p->next;
        } else {
            p2->next = p1;
            p2 = p1;
            p1 = p1->next;
        }
    }

    p2 = head2;
    printf("输出:");
    for (int i = 0; i < n+k; i++) {
        p2 = p2->next;
        printf("%d %c ", (p2->ID), (p2->name));
    }

}

可以先自己手动模拟一下例子，然后再用debug一步一步调试，这题大体上就分为3个模块，输入，合并，输出，每个模块依次调试，调试时注意变量的变化。

无序链表合并，修改如下，供参考：

#include <stdio.h>
#include <stdlib.h>
struct circle{
     int  ID;
     char name;
     struct circle* next;
};
int main()
{
    int n ,i;
    struct circle *p = NULL, *head = (struct circle *)malloc(sizeof(struct circle));
    head->next = NULL;
    p = head;
    printf("请输入表长:");
    scanf("%d", &n);
    for (i = 0;i < n; i++)
    {
        struct circle *s = (struct circle *)malloc(sizeof(struct circle));
        s->next = NULL;       // 修改
        printf("请输入ID:");
        scanf("%d", &s->ID);
        printf("请输入name:");
        scanf(" %c", &s->name);// 修改
        p->next = s;           // 修改
        p = s;                 // 修改
    }

    struct circle *p1 = NULL, *head1 = (struct circle *)malloc(sizeof(struct circle));
    head1->next = NULL;
    p1 = head1;
    printf("请输入表长:");
    scanf("%d", &n);
    for (i = 0;i < n; i++)
    {
        struct circle *s = (struct circle *)malloc(sizeof(struct circle));
        s->next = NULL;       // 修改
        printf("请输入ID:");
        scanf("%d", &s->ID);
        printf("请输入name:");
        scanf(" %c", &s->name);// 修改
        p1->next = s;          // 修改
        p1 = s;                // 修改
    }

    struct circle *p2 = NULL, *pt = NULL; // 修改
    p = head->next; p1 = head1->next;
    head->next = NULL;                    // 修改
    while (1)     // 修改
    {
        if (p)
        {
            pt = p;
            p = p->next;
            pt->next = NULL;
        }
        else if (p1){
            pt = p1;
            p1 = p1->next;
            pt->next = NULL;
        }

        if (!head->next)
            head->next = pt;
        else{
           p2 = head;
           while (p2->next && p2->next->ID > pt->ID)//学号降序
               p2 = p2->next;
           pt->next = p2->next;
           p2->next = pt;
        }
        if (!p && !p1) break;   // 修改
    }
    free(head1); // 修改

    printf("输出:");
    for (p2 = head->next;p2;p2 = p2->next)// 修改
        printf("%d %c ",p2->ID,p2->name);

    return 0;
}