一元多项式加法和乘法的链表实现

Question

02-线性结构2 一元多项式的乘法与加法运算 (20分)
设计函数分别求两个一元多项式的乘积与和。

输入格式:
输入分2行，每行分别先给出多项式非零项的个数，再以指数递降方式输入一个多项式非零项系数和指数（绝对值均为不超过1000的整数）。数字间以空格分隔。

输出格式:
输出分2行，分别以指数递降方式输出乘积多项式以及和多项式非零项的系数和指数。数字间以空格分隔，但结尾不能有多余空格。零多项式应输出0 0。

输入样例:

4 3 4 -5 2  6 1  -2 0
3 5 20  -7 4  3 1

输出样例:

15 24 -25 22 30 21 -10 20 -21 8 35 6 -33 5 14 4 -15 3 18 2 -6 1
5 20 -4 4 -5 2 9 1 -2 0

我的答案是

#include <stdio.h>
#include <stdlib.h>
typedef struct PolyNode *PolyNomial;
struct PolyNode{
  int coef;
  int expon;
  PolyNomial link;
};
void Attach(int c,int e,PolyNomial* prear){
  PolyNomial P;
  P=(PolyNomial)malloc(sizeof(struct PolyNode));
  P->link=NULL;
  P->coef=c;
  P->expon=e;
  (*prear)->link=P;
  *prear=P;
}
PolyNomial Add(PolyNomial L1,PolyNomial L2){
  PolyNomial t1,t2,rear,p,front;
  p=(PolyNomial)malloc(sizeof(struct PolyNode));
  p->link=NULL;
  rear=p;
  front=rear;
  if(!L1||!L2)return NULL;
  t1=L1;
  t2=L2;
  while(t1!=NULL&&t2!=NULL){
    if(t1->expon==t2->expon){
      int sum=t1->coef+t2->coef;
      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;
  }
  return front;
}
PolyNomial Multi(PolyNomial L1,PolyNomial L2){
  PolyNomial t1,t2,rear,p,front,t;
  int c,e;
  p=(PolyNomial)malloc(sizeof(struct PolyNode));
  p->link=NULL;
  rear=p;
  front=rear;
  t1=L1;
  t2=L2;
  while(t2){
    Attach(t1->coef*t2->coef,t1->expon+t2->expon,&rear);
  }
  t1=t1->link;
  while(t1){
    t2=L2;
    rear=p;
    while(t2){
      c=t1->coef*t2->coef;
      e=t1->expon+t2->expon;
      while(rear->link&&rear->link->expon>e){
        rear=rear->link;
      }
      if(rear->link&&rear->link->expon==e){
        if(rear->link->coef+c){
          rear->link->coef+=c;
        }
        else{
          t=rear->link;
          rear=rear->link;
          free(t);
        }
      }
      else{
        t=(PolyNomial)malloc(sizeof(struct PolyNode));
        t->coef=c;
        t->expon=e;
        t->link=rear->link;
        rear->link=t;
        rear=rear->link;
      }
      t2=t2->link;
    }
    t1=t1->link;
  }
  return front;
}
PolyNomial ReadPoly(){
  PolyNomial P,rear,t;
  P=(PolyNomial)malloc(sizeof(struct PolyNode));
  P->link=NULL;
  rear=P;
  int n,c,e;
  scanf("%d",&n);
  while(n--){
    scanf("%d %d",&c,&e);
    Attach(c,e,&rear);
  }
  t=P;
  P=P->link;
  free(t);
  return P;
}
void PrintPoly(PolyNomial P){
  printf("%d %d",P->coef,P->expon);
  P=P->link;
  while(P){
    printf(" %d %d",P->coef,P->expon);
  }  
}
int main(){
  PolyNomial L1,L2,m1,m2;
  L1=ReadPoly();
  L2=ReadPoly();
  m1=Multi(L1,L2);
  PrintPoly(m1);
  m2=Add(L1,L2);
  PrintPoly(m2);
}

编译后报错为

a.cpp: In function ‘PolyNode* ReadPoly()’:
a.cpp:105:17: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d",&n);
                 ^
a.cpp:107:25: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result]
     scanf("%d %d",&c,&e);

求大神指点为何scanf说返回值被忽视

Answer 1

编译的时候加一个-w就行了。