《数据结构》严蔚敏 算法2.22

用链表实现两个多项式相加

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

#define TRUE 1
#define FALSE 0
#define OK 1
#define ERROR 0
#define INFEASIBLE -1
#define OVERFLOW -2


typedef int Status;


typedef struct 
{
	int coef; //coefficient
	int expn; //exponent

}term,ElemType;

typedef struct LNode
{
	ElemType data;
	struct LNode *next;

}LNode,*Link,*Position;

typedef struct 
{
	Link head,tail; //just like two sides linklist
	int len;	

}LinkList; // Algorithm 2.20 define

typedef LinkList polynomial;

Status
InitList(LinkList *L)
{
	Link p;
	p = (Link)malloc(sizeof(LNode));
	if(!p)
		exit(OVERFLOW);
	L->head = L->tail = p;
	L->len = 0;
	p->next = NULL;
	return OK;
}

Position
GetHead(LinkList L)
{
	return L.head;
}

Status
SetCurElem(Link p,ElemType e)
{
	p->data = e;
	return OK;
}

ElemType
GetCurElem(Link p)
{
	return p->data;
}

Status
LocateElem(LinkList L,ElemType e,Position *q,int (*cmp)(ElemType,ElemType))
{
	Link p,pre;
	p = L.head;
	do
	{
		pre = p;
		p = p->next;

	}while( p != NULL && cmp(p->data,e) < 0);
	if( p == NULL || cmp(p->data,e) > 0)
	{
		*q = pre;
		return FALSE;
	}
	else
	{
		*q = p;
		return TRUE;
	}
}

int 
cmp(term a,term b)
{
	if(a.expn > b.expn)
		return 1;
	else if(a.expn == b.expn)
		return 0;
	else
		return -1;
}

Status
MakeNode(Link *p,ElemType *e)
{
	*p = (Link)malloc(sizeof(LNode));
	if(!*p)
		exit(OVERFLOW);
	(*p) -> data = *e;
	(*p) -> next = NULL;
	return OK;
}

Status
InsFirst(LinkList *L,Link h,Link *s) // Insert Node into the first address
{
	(*s) -> next = h -> next;
	h -> next = *s;
	L -> len++;
	if( h == L->tail)
		L->tail = h->next;
	return OK;
}


void CreatePolyn(polynomial * P,int m)
{
	Link h,q,s;
	term e;
	int i;

	
	InitList(P);
	h = GetHead(*P);
	e.coef = 0.0;
	e.expn = -1;
	SetCurElem(h,e);

	for(i = 0; i<m ; ++i)
	{
		printf("please enter %d coefficient and %d exponent: ",i,i);
		scanf("%d",&e.coef);
		scanf("%d",&e.expn);

		if(!LocateElem(*P,e,&q,cmp))
		{
			if(MakeNode(&s,&e))
				InsFirst(P,q,&s);
		}//if

	
	}//for


}


void
TraversePolyn(polynomial p)
{
	Link h;
	h = p.head -> next;
	printf("the polynomial is this:\n");
	while(h)
	{
		printf("%dx^%d",h->data.coef,h->data.expn);
		if(h->next)
			printf(" + ");
		h = h->next;
	}

	printf("\n");
}


Position
NextPos(LinkList L,Link p)
{
	return p->next;
}

Status
DelFirst(LinkList *L,Link h,Link *q)
{
	Link p;

    *q = h->next;
    h->next = (*q)->next;
    if(!h->next)
        (*L).tail = h;
    L->len--;
    return OK;
}

void FreeNode(Link p)
{
    p = NULL;
    free(p);
}



Status Append(LinkList *L,Link *s)
{
    int i = 0;
    (*L).tail->next = *s;
    while(*s){
        *s = (*s)->next;
        i++;
    }
    (*L).tail = *s;
    (*L).len += i;
    return OK;
}

Status ListEmpty(LinkList L)
{
    return (L.len == 0);
}


void
AddPolyn(polynomial *Pa,polynomial *Pb)
{
	Link ha,hb,qa,qb;
	term a,b;
	int sum;

	ha = GetHead(*Pa);
	hb = GetHead(*Pb);
	qa = NextPos(*Pa,ha);
	qb = NextPos(*Pb,hb); 

	while(qa && qb)
	{
		a = GetCurElem(qa);
		b = GetCurElem(qb);
		switch (cmp(a,b))
		{
			case -1:
				ha = qa;
				qa = NextPos(*Pa,qa);
				break;
			case 0:
				sum = a.coef + b.coef;
				if(sum != 0.0)
				{
					qa -> data.coef = sum;
					SetCurElem(qa,qa->data);
					ha = qa;
				}
				else
				{
					DelFirst(Pa,ha,&qa);
					FreeNode(qa);
				}
				DelFirst(Pb,hb,&qb);
	            FreeNode(qb);
	            qb = NextPos(*Pb,hb);
	            qa = NextPos(*Pa,ha);
	            break;
	        case 1:
	            DelFirst(Pb,hb,&qb);
	            InsFirst(Pa,ha,&qb);
	            qb = NextPos(*Pb,hb);
	            ha = NextPos(*Pa,ha);
	            break;
		}

	}

	if(!ListEmpty(*Pb))
			Append(Pa,&qb);
		FreeNode(hb);
}




int main(int argc, char const *argv[])
{
	
	polynomial Pa,Pb;

	printf("create unitary polynomial Pa: \n");
	CreatePolyn(&Pa,4);
	TraversePolyn(Pa);

	printf("\ncreate unitary polynomial Pb: \n");
	CreatePolyn(&Pb,3);
	TraversePolyn(Pb);

	printf("\nafter add two polynomials:\n");
	AddPolyn(&Pa,&Pb);
	TraversePolyn(Pa);

	return 0;
}