c0201时遇到的问题

多项式合并同类项，实现乘法加法

#include<stdio.h>#include<stdlib.h>struct PolyNode{    int coef;    int expon;    struct PolyNode* link;};typedef struct PolyNode *Polynomial;Polynomial ReadPoly(void);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 );    PS = Add(P1,P2);    printf("\n");    PrintPoly( PS );    while(1);    return 0;}Polynomial ReadPoly(){    Polynomial P,Rear,t;    int c,e,N;    scanf("%d",&N);    P = (Polynomial)malloc(sizeof(struct PolyNode)); /*链表头空结点*/    P->link = NULL;    Rear = P;    while(N--){        scanf("%d %d", &c, &e);        Attach(c,e,&Rear);   /*c函数的传值属性,由于Attach后Rear的值需要改变，所以一定是传入Rear的地址&*/    }    t = P; P = P->link; free(t);  /*删除临时生成的头结点*/    return P;}void Attach(int c, int e, Polynomial *pRear) /*pRear是指针的指针*/{    Polynomial P;    P = (Polynomial)malloc(sizeof(struct PolyNode));    P->coef = c;    P->expon = e;    P->link = NULL;    (*pRear)->link = P;    *pRear = P;   }Polynomial Add(Polynomial P1,Polynomial P2){    int sum ;                      /*一定要先全定义后，再赋值*/    Polynomial Rear,P,temp;        /*头结点，当前位置，返回的指针，插入时用来申请空间的结点，最后释放空结点的指针*/    Polynomial t1,t2;     /*先初始化！！！！！*/    t1 = P1; t2 = P2;    P = (Polynomial)malloc(sizeof(struct PolyNode));P->link=NULL;     Rear = P;   /*Rear指向尾巴*/    while(t1 && t2){        if(t1->expon == t2->expon){            sum = t1->coef + t2->coef;            if( sum ) Attach(sum, 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;    }    Rear->link = NULL;    temp = P;    P = P->link;    free(temp);    return P;         }Polynomial Mult(Polynomial P1,Polynomial P2){    Polynomial P,Rear,t1,t2,t;    int c,e;    if(!P1||!P2) return NULL; /*都为空*/    t1 = P1;t2 = P2;    P = (Polynomial)malloc(sizeof(struct PolyNode)); P->link = NULL;    Rear = P;    while(t2){        /*先用P1的第一项乘以P2，得到P,构造一个初始多项式*/        Attach(t1->coef*t2->coef,t1->expon+t2->expon,&Rear);        t2 = t2->link;    }    t1 = t1->link;    while(t1){ /*这个两重循环用t1的每一项乘t2的每一项*/        t2 = P2; Rear = P;/*重新赋值此时Rear和P指向的是头空结点*/        while(t2){            e = t1->expon + t2->expon;            c = t1->coef * t2->coef;    /*构造后如何插入*/            while( Rear->link && Rear->link->expon > e)                Rear = Rear->link;      /*找到Rear->link不大于插入项*/            if(Rear->link && Rear->link->expon == e){                if( Rear->link->coef+c)   /*非零项才插入*/                    Rear->link->coef += c;                else{                    t = Rear->link;                    Rear->link = t->link;                    free(t);    /*零项不插入 释放*/                }            }            else{   /*Rear->link->expon小于插入的项，那么直接插入到Rear的后面*/                t = (Polynomial)malloc(sizeof(struct PolyNode));                t->coef = c; t->expon = e;                t->link = Rear->link;                Rear->link = t; Rear = Rear->link; /*此为Insert不是Attach*/            }            t2 = t2->link;        }        t1 = t1->link;    }    /*对于最后的结果处理 合并同类项*/    t2 = P; P = P->link; free(t2); /*删除空头结点*/    return P;}void PrintPoly(Polynomial P){    int flag = 0;    /*辅助调整输出格式*/    if(!P){printf("0 0\n");return;}  /*P为空*/    while( P ){        if(!flag)            flag  = 1;        else            printf(" ");        printf("%d %d", P->coef, P->expon);        P = P->link;    }}