求链表中第i个结点的指针

link S =L;
int count = 0;
while(S!=NULL){
S = S->next;
count++;
if(count ==i)
break;
}
return S;

// 返回第pos个结点的地址，找不到时返回NULL
link solve(link & L, int i) {
    int index = 1;
    pNode p = L->next;
    while(p) {
        if(index == i) return p;
        p = p->next;
        ++index;
    }
    return NULL;
}