How to make the following program work? I think there are some place of the following program use the address NULL. But I don't know how to fix the problem. Thank you.
Code:#include <stdlib.h> #include <stdio.h> #include <string.h> #include <malloc.h> #include <math.h> typedef struct node /*a node denotes a P_{i,k}^{l}*/ { int l,i,k; } node; typedef struct monomial_node /* a monomial denotes a monomial P_{i,k}^{l} \cdots P_{i',k'}^{l'} */ { node y; int coeff; /* coeff is s(m_r) */ struct monomial_node *next; struct monomial_node *head; struct monomial_node *tail; } monomial_node, *monomial; typedef struct polynomial_node /* a polynomial denotes a sum of some monomials */ { monomial m; struct polynomial_node *next; struct polynomial_node *head; struct polynomial_node *tail; } polynomial_node, *polynomial; monomial insert(node a, monomial b) /* insert a factor a to a monomial b such that the first subscripts i's in the new monomial is in increasing order */ { monomial p; monomial_node *s; monomial_node *p1; p=b; p1=p->head->next; while((p1->y).i >= a.i) /* find the position */ { p1=p1->next; if(p1==p->tail) { break; } } if(p1==p->tail) { printf("tail\n"); } s=(monomial)malloc(sizeof(monomial_node)); /* create new node */ s->y=a; s->next=p1->next; /* insert the node a */ p1->next=s; return p; } monomial create_monomial(int number) /* create a monomial */ { monomial m,s; monomial p; int i; m=(monomial)malloc(sizeof(monomial_node)); m->head=m->tail=(monomial)malloc(sizeof(monomial_node)); if(m->head==NULL) { return NULL; } m->head->next=m->tail; m->tail->next=NULL; p=(monomial)malloc(sizeof(monomial_node)); m->head->next=p; p->next=m->tail; printf("Please input the parameters of the heighest weight monomial(for example, 2, 2, 3 denotes the monomial Y^{2}_{2,3}). The first subscripts i of Y's should be in increase order."); scanf("%d", &((p->y).l)); scanf("%d", &((p->y).i)); scanf("%d", &((p->y).k)); if(number > 1) { for(i=0;i<number-1;i++) { s=(monomial)malloc(sizeof(monomial_node)); scanf("%d", &((s->y).l)); scanf("%d", &((s->y).i)); scanf("%d", &((s->y).k)); m=insert(s->y,m); } } return m; } polynomial create_polynomial(monomial n) /* create a polynomial with only one monomial n */ { polynomial m,p; m=(polynomial)malloc(sizeof(polynomial_node)); p=(polynomial)malloc(sizeof(polynomial_node)); m->head=(polynomial)malloc(sizeof(polynomial_node)); m->tail=(polynomial)malloc(sizeof(polynomial_node)); m->head->next=p; p->m=n; p->next=m->tail; m->tail->next=NULL; return m; } void print_monomial(monomial m) { monomial p; p=(monomial)malloc(sizeof(monomial_node)); p=m->head->next; if(p==m->tail) { printf("No element. \n"); } while(p!=m->tail) { printf("Y^{%d}_{%d,%d}",(p->y).l,(p->y).i,(p->y).k); p=p->next; } } void print_polynomial(polynomial n) { polynomial p; int i=0; p=n->head->next; if(p==n->tail) { printf("No element. \n"); } while(p!=n->tail) { if(i !=0) { printf("+"); } i++; print_monomial(p->m); p=p->next; } printf("\n"); } int length_monomial(monomial a) { int len=0; monomial_node *b; b=a->head->next; while(b != a->tail) { len++; b=b->next; } return len; } int length_polynomial(polynomial a) { int len=0; polynomial_node *b; b=a->head->next; while(b != a->tail) { len++; b=b->next; } return len; } int compare_nodes(node a, node b) { int result; if(a.l==b.l && a.i==b.i && a.k==b.k) { result=1; } else { result=0; } return result; } monomial delete_node(node b, monomial a) { monomial p; monomial_node *p1; p=a; p1=p->head->next; p=p->head; while(p1 != a->tail) { if(compare_nodes(p1->y, b)==1) { p->next = p1->next; break; } p=p->next; p1=p1->next; } return p; } int main(int argc, char *argv[]) { node p; polynomial FM; polynomial new_monomials; polynomial phi[100][1000]; monomial s; monomial m; monomial mm[1000]; int type=1; int ra=2; int l; int i,j; int number; int a; int ccc[100][100]; printf("Please input the number of factors.\n"); scanf("%d", &number); m=create_monomial(number); FM=create_polynomial(m); print_monomial(m); printf("\n"); print_polynomial(FM); printf("\n len(m)=%d", length_monomial(m)); printf("\n len(FM)=%d", length_polynomial(FM)); node y,z,w; y.l=1;y.i=2;y.k=3; z.l=1;z.i=2;z.k=3; w.l=2;w.i=2;w.k=3; printf("\n y=z? %d\n", compare_nodes(y,z)); printf("\n y=w? %d\n", compare_nodes(y,w)); printf("\n delete y in m:\n"); print_monomial(delete_node(y, m)); return 0; }
