C 链表实现多项式

原来文章是用于转载，随笔才是原创，好吧，那发过来吧。

第一篇文章，如题用链表实现了多项式，包括输入、输出和三种运算。

这次代码主要遇到两个问题：scanf的连续调用，以及一个神奇的很不科学的bug——i的初始化问题

代码贴下来如下：

//本程序使用C语言创建一个链表来表示多项式
//多项式按照升序进行排列
//实现多项式的加、减、乘三个运算
#include<stdlib.h>
#include<stdio.h>
#define new(type) (type*)malloc(sizeof(type))
typedef struct _Term Term;
struct _Term{
float coef;
//系数
int exp;
//指数
Term *next;
};
Term* plus (Term* head1,Term* head2);
Term* minus(Term* head1,Term* head2);
Term* multi(Term* head1,Term* head2);
void print(Term* head);
void scan(Term* head);
int main(){
Term *head1 = new(Term);
head1->next = NULL;
Term *head2 = new(Term);
head2->next = NULL;
printf("Input format: coef,expn");
printf("Enter the ### to end the input.n");
printf("Input Polynomal 1:n");
scan(head1);
printf("Input Polynomal 2:n");
scan(head2);
Term * result1 = new(Term);
Term * result2 = new(Term);
Term * result3 = new(Term);
result1 = plus(head1,head2);
result2 = minus(head1,head2);
result3 = multi(head1,head2);
printf("result of plus:");
print(result1);
printf("result of minus:");
print(result2);
printf("result of multi:");
print(result3);
return 0;
}
void print(Term *head){
Term *temp = head->next;
while(temp != NULL){
if(temp->coef > 0)
printf("+%gx^%d",temp->coef,temp->exp);
else if(temp->coef < 0)
printf("%gx^%d",temp->coef,temp->exp);
temp = temp->next;
}
printf("n");
}
void scan(Term *head){
float coef;
int exp;
while(scanf("%f,%d",&coef,&exp) == 2){
Term *ptr = new(Term);
ptr->exp = exp;
ptr->coef = coef;
if(head->next == NULL){
ptr->next = NULL;
head->next = ptr;
}
else{
Term* temp = head->next;
Term* temp2 = head;
while(temp != NULL && temp->exp > ptr->exp){
temp = temp->next;
temp2 = temp2->next;
}
if(temp == NULL){
ptr->next = NULL;
temp2->next = ptr;
}
else{
ptr->next = temp2->next;
temp2->next = ptr;
}
}
}
while(getchar() != 'n');
return;
}
Term* plus(Term* head1,Term* head2){
Term *newhead = new(Term);
newhead->next = NULL;
Term *temp1 = head1->next;
Term *temp2 = head2->next;
Term *temp = newhead;
while(temp1 != NULL && temp2 != NULL){
Term *ptr = new(Term);
if(temp1->exp < temp2->exp){
ptr->next = NULL;
ptr->coef = temp2->coef;
ptr->exp = temp2->exp;
temp->next = ptr;
temp2 = temp2->next;
}
else if(temp1->exp > temp2->exp){
ptr->next = NULL;
ptr->coef = temp1->coef;
ptr->exp = temp1->exp;
temp->next = ptr;
temp1 = temp1->next;
}
else{
ptr->next = NULL;
ptr->coef = temp1->coef + temp2->coef;
ptr->exp = temp1->exp;
temp->next = ptr;
temp1 = temp1->next;
temp2 = temp2->next;
}
temp = temp->next;
}
if(temp1 == NULL){
while(temp2 != NULL){
Term *ptr = new(Term);
ptr->next = NULL;
ptr->coef = temp2->coef;
ptr->exp = temp2->exp;
temp->next = ptr;
temp2 = temp2->next;
temp = temp->next;
}
}
else if(temp2 == NULL){
while(temp1 != NULL){
Term *ptr = new(Term);
ptr->next = NULL;
ptr->coef = temp1->coef;
ptr->exp = temp1->exp;
temp->next = ptr;
temp1 = temp1->next;
temp = temp->next;
}
}
return newhead;
}
Term* minus(Term* head1,Term* head2){
Term *newhead = new(Term);
newhead->next = NULL;
Term *temp = newhead;
Term *temp2 = head2->next;
while(temp2 != NULL){
Term *ptr = new(Term);
ptr->next = NULL;
ptr->coef = -temp2->coef;
ptr->exp = temp2->exp;
temp->next = ptr;
temp2 = temp2->next;
temp = temp->next;
}
newhead =
plus(head1,newhead);
return newhead;
}
Term* multi(Term* head1,Term* head2){
int maxExp,i;
Term *newhead = new(Term);
newhead->next = NULL;
Term *temp = newhead;
Term *temp1 = head1->next;
Term *temp2 = head2->next;
if(temp1 != NULL && temp2 != NULL)
maxExp = temp1->exp + temp2->exp;
printf("maxExp:%dn",maxExp);
float *result = malloc(sizeof(float) * (maxExp+1));
i = 0;
while(i <= maxExp){
result[i] = 0.0;
i ++;
}
while(temp1 != NULL){
temp2 = head2->next;
while(temp2 != NULL){
i = temp1->exp + temp2->exp;
printf("exp:%d,%dn",temp1->exp,temp2->exp);
printf("coef:%f,%fn",temp1->coef,temp2->coef);
printf("result:%f",result[i]);
result[i] = result[i] + temp1->coef * temp2->coef;
printf("result[%d]=%fn",i,result[i]);
temp2 = temp2->next;
}
temp1 = temp1->next;
}
for(i = maxExp; i >= 0; i --){
if(result[i] != 0){
Term *ptr = new(Term);
ptr->next = NULL;
ptr->coef = result[i];
ptr->exp = i;
temp->next = ptr;
temp = temp->next;
}
}
free(result);
return newhead;
}

先说第一个问题，在连续两次使用scanf的时候，发现总是第二个scanf不能获取输入。

查阅网上相关资料后明白了其中的原理，现在举例如下：

第一次使用scanf("%dn",&i);

你会有类似这样的输入：1n，这里问题的关键就在于第二个字符，回车，他还留在缓存区的，

这样当你第二次调用scanf()的时候，他会先读取回车自然就不能继续输入了，

解决这个问题只需要添加一句getchar()，将其从缓存区取出，就能解决了。

第二个不科学的bug，我至今也没有想明白，就是在169行，最开始我没有初始化i，那么在main函数中的调用肯定错误

但是当我在调用之前，加上一句printf("xxxx");后他就神奇的对了，至今不明白，希望懂的人赐教。