阅读以下应用说明、图和C++程序，将C++程序中(1)～(6)空缺处的语句填写完整。【说明】以下【C++程序】用于实现两个多项式的乘积运算。多项式的每一项由类Item描述，而多项式由类List描述。类List的成员函数主要有：createList()：创建按指数降序链接的多项式链表，以表示多项式：reverseList()：将多项式链表的表元链接顺序颠倒：multiplyList(ListL1，ListL2)计算多项式L1和多项式L2的乘积多项式。【C++程序】include ＜iostream.h＞class List;class Item {friend class List;private:double quot ;int exp ;Item *next;Public:Item(double_quot,int_exp){ (1) ;}};class List{private:Item *list;Public:List(){list=NULL:}void reverseList();void multiplyList(List L1,List L2);void createList();};void List::createList(){ Item *p,*U,*pre;int exp;double quot;list = NULL;while (1) {cout ＜＜ '输入多项式中的一项(系数、指数) :' ＜＜ endl;cin ＞＞ quot ＞＞ exp:if ( exp＜0 )break ; //指数小于零，结束输入if ( quot=0 )continue;p = list;while ( (2) ) { //查找插入点pre = p;p = p-＞next;}if ( p != NULL && exp = p-＞exp ) {p-＞quot += quot;continue ;}u =(3);if (p == list)list = u;elsepre-＞next = u;u -＞next = p;}}void List::reverseList(){ Item *p, *u;if ( list==NULL )return;p = list -＞next;list -＞ next = NULL;while ( p != NULL) {u = p -＞ next;p -＞next = list;list = p;p = u;}}void List::multiplyList ( List L1, List L2 ){ Item *pL1,*pL2,*u;int k, maxExp;double quot;maxExp =(4):L2.reverseList();list=NULL;for ( k = maxExp;k ＞= 0;k-- ){pL1 = L1.list;while ( pL1 != NULL && pL1 -＞ exp ＞ k )pL1 = pL1 -＞next;pL2 = L2.1ist;while (pL2 NULL &&(5))pL2 = pL2 -＞ next;quot = 0.0;while (pL1 != NULL && pL2 != NULL){if(pL1-＞exp+pL2-＞exp==k) {(6)pL1 = pL1 -＞ next;pL2 = pL2 -＞ next;} else if ( pL1 -＞ exp + pL2 -＞ exp ＞ k )pL1 = pL1 -＞ next;elsepL2 = pL2 -＞ next;}if ( quot !=0.0 ) {u = new item( quot, k );u -＞ next = list;list = u;}}reverseList ();L2. reverseList ():}void main(){ List L1,L2,L;

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