[刷题] 多项式加法、乘法

mooc例题

#include<stdio.h>
#include<malloc.h>
#include<string.h>
#include<time.h>
#include<math.h>

//指向结构体头节点的指针 
typedef struct PolyNode *Polynomial;

struct PolyNode{
    int coef;
    int expon;
    Polynomial link;
};

Polynomial ReadPoly();
void Attach(int c,int e,Polynomial *pRear);
Polynomial Add(Polynomial P1,Polynomial P2);
Polynomial Mult(Polynomial P1,Polynomial P2);
void PrintPoly(Polynomial P);

int main(){
    Polynomial P1,P2,PP,PS;
    P1 = ReadPoly();
    P2 = ReadPoly();
    PP = Mult(P1,P2);
    PrintPoly(PP);
    printf("
");
    PS = Add(P1,P2);
    PrintPoly(PS);
    return 0;
}

/*读入多项式*/ 
Polynomial ReadPoly(){
    Polynomial P,Rear,t;    /*Rear为指向当前结果尾项的指针*/ 
    int c,e,N;
    scanf("%d",&N);
    P = (Polynomial)malloc(sizeof(struct PolyNode));    /*申请空节点*/ 
    P->link = NULL;
    Rear = P;    /*初始化，Rear指向空节点*/
    while(N--){
        scanf("%d%d",&c,&e);
        Attach(c,e,&Rear);        /*增加一项*/ 
    } 
    t = P;P = P->link;free(t);    /*删除临时生成的头节点*/ 
    return P;
}

/*插入新节点*/ 
/*更改Rear的值，传入指针*/ 
void Attach(int c,int e,Polynomial *pRear){
    Polynomial P;
    P = (Polynomial)malloc(sizeof(struct PolyNode));
    P->coef = c;    
    P->expon = e;
    P->link = NULL;        /*Rear指向空节点*/ 
    (*pRear)->link = P;        /*pRear是指针的指针*/ 
    *pRear = P;        /*修改pRear的值*/ 
}

Polynomial Add(Polynomial P1,Polynomial P2){
    Polynomial t1,t2,P,Rear,t;
    t1 = P1;t2 = P2;
    /*当生成新的头节点*/ 
    P = (Polynomial)malloc(sizeof(struct PolyNode));
    P -> link = NULL;
    Rear = P;
    /*当t1,t2都不空时，比较当前t1,t2的指数*/ 
    while(t1 && t2){
        if(t1->expon == t2->expon){
            if(t1->coef + t2->coef){
                Attach(t1->coef + t2->coef,t1->expon,&Rear);
            }
            t1 = t1->link;
            t2 = t2->link;
        }
        else if(t1->expon > t2->expon){
        Attach(t1->coef,t1->expon,&Rear);
        t1 = t1->link;
        }
        else{
        Attach(t2->coef,t2->expon,&Rear);
        t2 = t2->link;
        }
    }
    while(t1){
        Attach(t1->coef,t1->expon,&Rear);
        t1 = t1->link;
    }
    while(t2){
        Attach(t2->coef,t2->expon,&Rear);
        t2 = t2->link;
    }
    t = P;
    P = P->link;
    free(t);
    return P;
}

Polynomial Mult(Polynomial P1, Polynomial P2)
{
    Polynomial P, Rear;
    Polynomial t1, t2, t;
    if (!P1 ||!P2)
    {
        return NULL;

    }
    t1 = P1;
    t2 = P2;
    P = (Polynomial)malloc(sizeof(struct PolyNode));
    Rear = P;
    while (t2)        /*用P1的第一项乘以P2，得到初始P*/ 
    {
        Attach(t1->coef*t2->coef, t1->expon + t2->expon, &Rear);
        t2 = t2->link;
    }
    t1 = t1->link;

    while (t1)        /*t1的第一项后的每一项乘以t2的每一项*/
    {
        t2 = P2;    /*每循环一遍要使指针回到首节点*/
        Rear = P;    /*将尾节点置到头结点*/
        while (t2) 
        {
            int c = t1->coef*t2->coef;        /*以后每一项相乘的结果*/
            int e = t1->expon + t2->expon;
            while (Rear->link&&Rear->link->expon > e)    /*找插入的位置*/
            {
                Rear = Rear->link;
            }
            if (Rear->link&&Rear->link->expon == e)        /*相等就不需要申请一个新的节点，只要把系数相加*/
            {
                if (Rear->link->coef + c)    /*判断系数是否为0*/
                {
                    Rear->link->coef += c;
                }
                else    /*系数和为0，删除节点*/
                {
                    t = Rear->link;
                    Rear->link = t->link;
                    free(t);
                }
            }
            else    /*不相等，也就是小于的情况*/
            {
                t = (Polynomial)malloc(sizeof(struct PolyNode));    /*申请一个新的节点*/
                t->link = NULL;
                t->coef = c;
                t->expon = e;
                t->link = Rear->link;
                Rear->link = t;
                Rear = Rear->link;
            }
            t2 = t2->link;
        }
        t1 = t1->link;
    }
    /*把一开始申请的内容空P的指针删除，指向下一个位置*/
    t2 = P;
    P = P->link;
    free(t2);
    return P;
}

void PrintPoly(Polynomial P)
{
    int flag = 0;    /*辅助调整输出格式*/
    if (!P)
    {
        printf("0 0");
        return;
    }
    while (P)
    {
        if (!flag)        /*可以看做系数 指数 ，空格 系数 指数，空格 系数 指数。。。。。。用flag标记第一次*/
        {
            flag = 1;

        }
        else    /*不是第一项*/
        {
            printf(" ");
        }
        printf("%d %d", P->coef, P->expon);
        P = P->link;
    }
}