c语言编程实现一元多项式的加法运算

#include <stdio.h>
#include <stdlib.h>

typedef struct PolyNode *Polynomial;
struct PolyNode{
    int coef; // 系数
    int expon; // 指数
    Polynomial link; // 下一项
};

void Attach(int c, int e, Polynomial *pRear){
    Polynomial P;

    // 新建节点
    P = (Polynomial)malloc(sizeof(struct PolyNode));
    P->coef = c;
    P->expon = e;
    P->link = NULL;

    // 插入节点
    (*pRear)->link = P;
    *pRear = P;
}

Polynomial PolyAdd(Polynomial P1, Polynomial P2){
    Polynomial P, Rear, t1, t2;
    int sum;

    // 新建头节点
    P = (Polynomial)malloc(sizeof(struct PolyNode));
    Rear = P;

    t1 = P1->link;
    t2 = P2->link;

    while(t1 && t2){
        if(t1->expon == t2->expon){ // 指数相等
            sum = t1->coef + t2->coef;
            if(sum) // 系数不为0
                Attach(sum, t1->expon, &Rear);
            t1 = t1->link;
            t2 = t2->link;
        }
        else if(t1->expon > t2->expon){ // P1中指数较大
            Attach(t1->coef, t1->expon, &Rear);
            t1 = t1->link;
        }
        else{ // P2中指数较大
            Attach(t2->coef, t2->expon, &Rear);
            t2 = t2->link;
        }
    }

    // 将未处理完的项接到结果多项式中
    for(; t1; t1 = t1->link)
        Attach(t1->coef, t1->expon, &Rear);
    for(; t2; t2 = t2->link)
        Attach(t2->coef, t2->expon, &Rear);

    // 删除头节点
    Rear->link = NULL;
    P = P->link;
    free(P1);
    free(P2);

    return P;
}

void PrintPoly(Polynomial P){
    if(!P){
        printf("0 0\n");
        return;
    }

    while(P){
        printf("%d %d", P->coef, P->expon);
        P = P->link;
        if(P)
            printf(" ");
    }
    printf("\n");
}

int main(){
    Polynomial P1, P2, PP, PS;

    // 新建多项式P1
    P1 = (Polynomial)malloc(sizeof(struct PolyNode));
    P1->link = NULL;
    Attach(5, 0, &P1);
    Attach(2, 1, &P1);
    Attach(-3, 2, &P1);

    // 新建多项式P2
    P2 = (Polynomial)malloc(sizeof(struct PolyNode));
    P2->link = NULL;
    Attach(7, 1, &P2);
    Attach(-2, 2, &P2);
    Attach(4, 4, &P2);

    // 输出多项式P1和P2
    printf("P1: ");
    PrintPoly(P1);
    printf("P2: ");
    PrintPoly(P2);

    // 多项式相加
    PP = PolyAdd(P1, P2);

    // 输出相加结果
    printf("P1 + P2: ");
    PrintPoly(PP);

    return 0;
}