数据结构05-多项式的加法

add函数中，在老师的基础上看同学的改法改了一个括号，在while的最后只要p ！= NULL，就让r->next指向p是没有问题的。q = NULL时自不必说，q ！= NULL时下一个while循环也会让r或者r->next指向正确的地方。

void add(LinkList pList1,LinkList pList2){
	NodePtr p,q,r,s;
	
	p = pList1->next;
	q = pList2->next;
	r = pList1;
	
	free(pList2);
	
	while((p != NULL) && (q != NULL)){
		if(p->exponent < q->exponent){
			r = p;
			p = p->next;
		}else if((p->exponent > q->exponent)){
			r->next = q;
			r = q;
			q = q->next;
		}else{
			p->coefficient = p->coefficient + q->coefficient;
			printf("The coefficient is: %d.\n",p->coefficient);
			if(p->coefficient == 0){
				s = p;
				p = p->next;
				free(s);
			}else{
				r = p;
				p = p->next;
			}
			s = q;
			q = q->next;
			free(s);
		}
		printf("p = %d,q = %d \n",p,q);

		if(p == NULL){
			r->next = q;
		}else { 
			r->next = p;
		}
	}
}

完整代码

#include 
#include 

typedef struct LinkNode{
	int coefficient;
	int exponent;
	struct LinkNode *next;
} *LinkList,*NodePtr;

LinkList iniLinkList(){
	LinkList Header = (LinkList)malloc(sizeof(struct LinkNode));
	Header->coefficient =  0;
	Header->exponent = 0;
	Header->next = NULL;
	return Header;
}

void printList(LinkList pHeader){
	NodePtr p = pHeader->next;
	while(p != NULL){
		printf("%d * 10^%d +",p->coefficient,p->exponent);
		p = p->next;
	}
	printf("\n");
}

void appendElement(LinkList pHeader,int pCoefficient,int pExponent){
	NodePtr p,q;
	
	q = (NodePtr)malloc(sizeof(struct LinkNode));
	q->coefficient = pCoefficient;
	q->exponent = pExponent;
	q->next =NULL;
	
	p = pHeader;
	while(p->next != NULL){
		p = p->next;
	}
	
	p->next = q;
}

void add(LinkList pList1,LinkList pList2){
	NodePtr p,q,r,s;
	
	p = pList1->next;
	q = pList2->next;
	r = pList1;
	
	free(pList2);
	
	while((p != NULL) && (q != NULL)){
		if(p->exponent < q->exponent){
			r = p;
			p = p->next;
		}else if((p->exponent > q->exponent)){
			r->next = q;
			r = q;
			q = q->next;
		}else{
			p->coefficient = p->coefficient + q->coefficient;
			printf("The coefficient is: %d.\n",p->coefficient);
			if(p->coefficient == 0){
				s = p;
				p = p->next;
				free(s);
			}else{
				r = p;
				p = p->next;
			}
			s = q;
			q = q->next;
			free(s);
		}
		printf("p = %d,q = %d \n",p,q);
	
		if(p == NULL){
			r->next = q;
		}else{
			r->next = p;
		}
	}
}

void addTest(){
	LinkList tempList1 = iniLinkList();
	appendElement(tempList1,7,0);
	appendElement(tempList1, 3, 1);
	appendElement(tempList1, 9, 8);
	appendElement(tempList1, 5, 17);
	printList(tempList1);
	
	LinkList tempList2 = iniLinkList();
	appendElement(tempList2, 8, 1);
	appendElement(tempList2, 22, 7);
	appendElement(tempList2, -9, 10);
	appendElement(tempList2, 5, 12);
	printList(tempList2);

	add(tempList1, tempList2);
	printList(tempList1);
}

int main(){
	addTest();
	return 0;
}

运行结果

7 * 10^0 +3 * 10^1 +9 * 10^8 +5 * 10^17 +
8 * 10^1 +22 * 10^7 +-9 * 10^10 +5 * 10^12 +
p = 7607440,q = 7629504
The coefficient is: 11.
p = 7607472,q = 7629536
p = 7607472,q = 7629568
p = 7607504,q = 7629568
p = 7607504,q = 7629600
p = 7607504,q = 0
7 * 10^0 +11 * 10^1 +22 * 10^7 +9 * 10^8 +-9 * 10^10 +5 * 10^12 +5 * 10^17 +