单向循环链表删除首结点，成功返回true，失败返回false

/*
 * ==============================================================
 * File name:        del_first_node_in_circular_list.c
 * Author:           3360652783@qq.com
 * Date created:     2026-07-23
 * Description:      Delete the first node in a circular singly linked list with head node.
 * Copyright notice: All right Reserved
 * ==============================================================
 */

//构建删除单向循环链表首结点的函数
bool FirstNode_del(*L)(){
    CirLinkList *P;                 //用于暂存当前结点
    if( L->next == L ){             //如果是个空表，则删除失败
        return false;
    }
    p = L->next;
    while( p->next != L->next ){        //遍历找到最后一个结点
        p = p->next;
    }
    p->next = L->next->next;         //将最后结点的指针指向第二个结点
    p = L->next;                     //重复利用变量p，用于释放第一个结点的空间
    L->next = p->next;
    p->next = NULL;
    free(p);
    if( L->next == NULL ){          //如果删除首结点后仅剩头结点，则头结点的指针指向自己
        L->next = L;
    }
    return true;
}