算法设计题：设文件R1 R2 … Rn以单链表方式存储指针变量FIRST指向表头结点结点结构为KEY LINK给出该种线性表的直接选择排序c语言算法

void selectionSort(Node *first) { Node *p, *q, *r, *s; for (r = first; r->link != NULL; r = r->link) { for (p = q = r, s = r->link; s != NULL; p = s, s = s->link) { if (s->key < q->key) { q = s; r->link = s; } } if (q != r) { p->link = q->link; q->link = r->link; r->link = q; } } }