?值得一提的是，在整個加法插入中，我們只需遍歷一次多項式，便可以整個加法運算，因為輸入的項的指數(shù)是按從高到低的順序

因為這塊是難點重點，所以稍微總結(jié)一下：
?我們首先傳入power，通過它來尋找一個合適的位置，傳入的head便是從head指向的節(jié)點開始向后尋找（第一次使用這個函數(shù)傳入的head都是指向頭節(jié)點的）
?在尋找的過程中if (temp->power == power || temp->next == 0)，便返回temp；if(temp->next->power >= power)，便更新temp，否則便表示結(jié)果是需要在temp后面插入節(jié)點，返回temp；

void insert(int * isInsert, Pnode head1, Pnode head2)：將項插入節(jié)點后面后者修改該節(jié)點
?這里可以解釋isInsert的作用，如果表示插入，那么我們便會把isInsert改成1，表示頭結(jié)點的非零項的數(shù)目需要++；如果表示修改，便查看修改后的系數(shù)是否等于零，如果為零，便會改成1。表示需要將非零項的個數(shù)--；若不等于零便會改成0，不需要修改非零項的個數(shù)

Pnode multi(Pnode head1, Pnode head2)：核心和加法運算大致相同，只是多了一層二重循環(huán)，來執(zhí)行乘法，看懂了上面仔細閱讀即可了解

void printResult(Pnode head)：輸出結(jié)果

Code

#include<stdio.h>
#include<malloc.h>
typedef struct node {
    int coust;
    int power;
    struct node* next;
}Node, *Pnode;
Pnode createList(void);
Pnode copyList(Pnode head);
void add(Pnode head1, Pnode head2);
Pnode multi(Pnode head1, Pnode head2);
void printResult(Pnode head);
Pnode findEle(int power, Pnode head);
void insert(int * isInsert, Pnode head1, Pnode head2);
int main(void) {
    Pnode poly1 = createList();
    Pnode poly2 = createList();
    Pnode addPoly = copyList(poly1);

    Pnode multiPoly = multi(poly1, poly2);
    add(poly2, addPoly);
    printResult(multiPoly);
    printResult(addPoly);
    return 0;
}
Pnode createList(void) {
    Pnode temp = 0;
    Pnode head = temp = (Pnode)malloc(sizeof(Node));
    head->power = 9999;
    int length;
    scanf("%d",&length);
    head->coust = length;
    for (int i = 0; i < length; i++) {
        temp->next = (Pnode)malloc(sizeof(Node));
        temp =  temp->next;
        scanf("%d %d",&temp->coust, &temp->power);
        temp->next = 0;
    }
    return head;
}
Pnode copyList(Pnode head) {
    Pnode tempOfHead = head;
    Pnode tempOfHead1 = 0;
    Pnode head1 = tempOfHead1 = (Pnode)malloc(sizeof(Node));
    head1->power = head->power;
    int length = head1->coust = head->coust;
    for (int i = 0; i < length; i++) {
        tempOfHead1->next = (Pnode)malloc(sizeof(Node));
        tempOfHead1 = tempOfHead1->next;
        tempOfHead = tempOfHead->next;
        tempOfHead1->coust = tempOfHead->coust;
        tempOfHead1->power = tempOfHead->power;
        tempOfHead1->next = 0;
    }
    return head1;
}
void add(Pnode head1, Pnode head2) {
    Pnode temp1 = head1->next;
    Pnode temp2 = head2;
    Pnode temp = 0;
    int isInsert = 0;
    for (;temp1 != 0;) {
        temp2 = findEle(temp1->power, temp2);
        insert(&isInsert, temp1, temp2);
        if (isInsert == 1) {
            head2->coust++;
        }
        else if (isInsert == -1) {
            head2->coust--;
        }
        temp1 = temp1->next;
    }
}
Pnode multi(Pnode head1, Pnode head2) {
    Pnode temp1 = head1;
    Pnode temp2 = head2;
    Pnode multi = (Pnode)malloc(sizeof(Node));
    Pnode temp3 = 0;
    Pnode temp = 0;
    multi->coust = 0;
    multi->next = 0;
    multi->power = 9999;
    if (head1->coust == 0 || head2->coust == 0) {
        return multi;
    }
    else {
        temp1 = head1->next;
        //temp2 = head2->next;
        int isInsert = 0;
        for (; temp1 != 0; temp1 = temp1->next) {
            temp2 = head2->next;
            temp3 = multi;
            for (; temp2 != 0; temp2 = temp2->next) {
                temp = (Pnode)malloc(sizeof(Node));
                temp->power = temp1->power + temp2->power;
                temp->coust = temp1->coust * temp2->coust;
                temp->next = 0;
                temp3 = findEle(temp->power, temp3);
                insert(&isInsert, temp, temp3);
                if (isInsert == 1)
                    multi->coust++;
                else if (isInsert == -1)
                    multi->coust--;
                free(temp);
            }
        }
    }
    return multi;
}
void printResult(Pnode head) {
    if (head->coust == 0) {
        printf("%d %d", 0, 0);
    }else
    {
        Pnode  temp = head->next;
        printf("%d %d", temp->coust, temp->power);
        temp = temp->next;
        for (;temp != 0; temp = temp->next) {
            if (temp->coust == 0) {
                continue;
            }else {
                printf(" %d %d", temp->coust, temp->power);
            }
        }
    }
    printf("\n");
}
Pnode findEle(int power, Pnode head) {
    Pnode temp = head;
    for (; temp!= 0;) {
        if (temp->power == power || temp->next == 0) {
            return temp;
        }
        else {
            if(temp->next->power >= power)
                temp = temp->next;
            else
                return temp;
        }
    }
    return temp;
}
void insert(int * isInsert, Pnode head1, Pnode head2) {
    if (head2->power == head1->power) {
        head2->coust += head1->coust;
        if (head2->coust == 0) {
            *isInsert = -1;
            //if(head2->next != 0)
                //head2->next = head2->next->next;
            
            return;
        }
        *isInsert = 0;
    }else {
            Pnode temp = (Pnode)malloc(sizeof(Node));
            temp->coust = head1->coust;
            temp->power = head1->power;
            temp->next = head2->next;
            head2->next = temp;
            *isInsert = 1;      
    }
}

Summary

?總體感覺還是有些難度的，主要難點在于findEle中，因為有幾種尋找方式，不同的尋找方式會導(dǎo)致insert操作會有所不同
?而且有些查找方式不能很好的照顧到邊界情況，例如在第一個節(jié)點前面插入一個節(jié)點，最后一個節(jié)點后面插入一個節(jié)點，或者不同的終止條件會造成可能不能遍歷最后一個節(jié)點等等,如果不仔細想好合適的查找方式，很容易不能照顧到邊界情況
?還要說一點，還是要多考慮極限情況才能比較順暢的答題，否則很容易陷入打補丁式的編寫