#include <stdio.h> #include <stdlib.h> //比较函数返回值 #define A_EQUAL_B  0 #define A_LARGE_B  1 #define A_LOWER_B -1 //错误返回之集合 #define SUCCESS            0 #define POINT_ARG_IS_NULL -1 #define LINKLIST_IS_NULL  -2 #define NOT_FOUND         -3 typedef struct {     int cst_term;//常数项     int idx_term;//指数 }factor; typedef factor data_t; typedef struct linklist {  data_t data;  struct linklist *next; }linklist; /*  *  * malloc头节点，头节点内的数据是无效的  *  */ linklist *creat_lnklst() {  linklist *head = (linklist *)malloc(sizeof(linklist));  head->next = NULL;  return head; } /*  * pll是插入节点的前一项  * data是数据  * 为新节点分配内存，之后插入  *  */ int ins_head_lnklst(linklist *pll, const data_t *data) {  linklist *newnode = NULL;  if(NULL == pll || NULL == data)   return POINT_ARG_IS_NULL;  newnode = (linklist *)malloc(sizeof(linklist));  newnode->data = *data;  newnode->next = pll->next;  pll->next = newnode;  return SUCCESS; } /*  *  * pll是要删除节点的前一个  * data存放删除的数据  * 检查pll是否是空  * 检查链表是否为空  * data是NULL就不用保存删除的数据  *  */ int del_head_lnklst(linklist *pll, data_t *data) {  linklist *tmp = NULL;  if(NULL == pll)   return POINT_ARG_IS_NULL;  if(pll->next == NULL)   return LINKLIST_IS_NULL;  tmp = pll->next;  if(NULL != data)   *data = tmp->data;  pll->next = tmp->next;  free(tmp);  return SUCCESS; } /*  *  * 内部支持data_t大小比较函数  * 如果data_t修改成其他类型则需要修改此方法  *  */ static int cmp_data(const data_t *a, const data_t *b) {  int res = 0;  if(a == NULL || b == NULL)   return POINT_ARG_IS_NULL;  res = a->idx_term - b->idx_term;  if(res == 0)   return A_EQUAL_B;  else if(res > 0)   return A_LARGE_B;  else   return A_LOWER_B; } /*  *  * 实现在链表中查找data匹配的前一项  * compare是实现虚拟数据类型比较函数  *  */ linklist * locate_lnklst(linklist *pll, const data_t *data, int (*compare)(const data_t *, const data_t *)) {  if(NULL == pll || data == NULL)   return NULL;  if(NULL == compare)   compare = cmp_data;  while(pll->next)  {   if(A_EQUAL_B == compare(&(pll->next->data), data))    return pll;   pll = pll->next;  }  return NULL; } /*  *  * 打印链表数据  * 检查参数空指针  * 检查空链表  *  */ int print_lnklst(linklist *pll) {  if(NULL == pll)   return POINT_ARG_IS_NULL;  if((pll = pll->next) == NULL)  {   printf("%s\n", "no element in linklist.\n");   return LINKLIST_IS_NULL;  }  while(pll)  {         if(pll->next == NULL)         {       printf("%2d*X^ ", pll->data.cst_term, pll->data.idx_term);         }         else         {       printf("%2d*X^ +", pll->data.cst_term, pll->data.idx_term);         }   pll = pll->next;  }  printf("\n");  return SUCCESS; } /*  *  * 删除对应数据的节点  *  */ int locate_del_lnklst(linklist *pll, const data_t *data) {  linklist *prev = NULL;  if(NULL == pll || data == NULL)   return POINT_ARG_IS_NULL;  prev = locate_lnklst(pll, data, NULL);  if(NULL == prev)   return NOT_FOUND;  return del_head_lnklst(prev, NULL); } int add_linklist(linklist *a, linklist *b) {     linklist *tmp;     if(NULL == a || NULL == b)         return POINT_ARG_IS_NULL;     if((b = b->next) == NULL)     {         return LINKLIST_IS_NULL;     }     while(b != NULL)     {         tmp = locate_lnklst(a, &b->data, NULL);         if(NULL == tmp)             ins_head_lnklst(a, &b->data);         else             tmp->next->data.cst_term += b->data.cst_term;         b = b->next;     }     return 0; } /*  *  * A = 1 + 2*X + 3*X^2  * B = 4 + 5*X + 6*X^2  * R = A + B  *   = 5 + 7*X + 9*X^2  *  */ int init_a_b(linklist *a, linklist *b) {     factor tmp;     tmp.cst_term = 1;     tmp.idx_term = 0;     ins_head_lnklst(a, &tmp);     tmp.cst_term = 2;     tmp.idx_term = 1;     ins_head_lnklst(a, &tmp);     tmp.cst_term = 3;     tmp.idx_term = 2;     ins_head_lnklst(a, &tmp);     tmp.cst_term = 4;     tmp.idx_term = 0;     ins_head_lnklst(b, &tmp);     tmp.cst_term = 5;     tmp.idx_term = 1;     ins_head_lnklst(b, &tmp);     tmp.cst_term = 6;     tmp.idx_term = 2;     ins_head_lnklst(b, &tmp);     return 0; } int main(int argc, const char *argv[]) {  linklist *fml_a = creat_lnklst();  linklist *fml_b = creat_lnklst();     init_a_b(fml_a, fml_b);     printf("A =");     print_lnklst(fml_a);     printf("B =");     print_lnklst(fml_b);     add_linklist(fml_a, fml_b);     printf("A + B =");     print_lnklst(fml_a);  return 0; }