二叉树计算中缀表达式

         二叉树计算中缀表达式，暂时不支持括号，直接以字符串形式输入。

#include <stdio.h>#include <conio.h>#include <stdlib.h>#include <malloc.h>typedef struct tagbintree{ char op; char level; /* 记录括号 */ double fvalue; struct tagbintree *lchild; struct tagbintree *rchild;}bintree;char getlevel(char op);int isop(char c);double caltree(const bintree *node);void distree(const bintree *node);void destorytree(bintree **node);void appendnode(bintree **node, char op, double value);bintree *createtree(const char *szexpress);int main(void){ bintree *root; root = createtree("12*15"); distree(root); printf("\n=%lf\n\n", caltree(root)); destorytree(&root); root = createtree("-12+390.564*56*78-90/18.56*129.35+86.073+1345.302+10.9301*99.01"); distree(root); printf("\n=%lf\n", caltree(root)); destorytree(&root); getch();}void distree(const bintree *node){ if (node == NULL)  return; distree(node->lchild); distree(node->rchild); if (node->op != 0)  printf("%c ", node->op); else  printf("%f ", node->fvalue);}void destorytree(bintree **node){ if (*node == NULL)  return; if ((*node)->lchild != NULL)  destorytree(&(*node)->lchild); if ((*node)->rchild != NULL)  destorytree(&(*node)->rchild); free(*node); *node = NULL;}void appendnode(bintree **node, char op, double value){ bintree *node1; bintree *node2; node1 = (bintree *)malloc(sizeof(bintree)); node1->op = op; node1->level = getlevel(op); node1->fvalue = 0; node2 = (bintree *)malloc(sizeof(bintree)); node2->op = 0; node2->level = getlevel(node2->op); node2->fvalue = value; node2->lchild = NULL; node2->rchild = NULL; node1->rchild = node2; if ((*node)->level != 0 && node1->level > (*node)->level)  {   bintree *childnode = *node;   node1->lchild = (*node)->rchild;   (*node)->rchild = node1;  } else  {   node1->lchild = *node;   *node = node1;  }}char getlevel(char op){ if (op == 0)  return 0; if (op == '*' || op == '/')  return 2; if (op == '+' || op == '-')  return 1;}int isop(char c){ if (c == '+' || c == '-' || c == '*' || c == '/')  return 1; return 0;}double caltree(const bintree *node){ if (node->op == 0)  return node->fvalue; if (node->op == '*')  return caltree(node->lchild) * caltree(node->rchild); if (node->op == '/')  return caltree(node->lchild) / caltree(node->rchild); if (node->op == '+')  return caltree(node->lchild) + caltree(node->rchild); if (node->op == '-')  return caltree(node->lchild) - caltree(node->rchild);}bintree *createtree(const char *szexpress){ const char *ptr = szexpress; char op; static char numstr[1024] = {"0"}; char *ptrnum = numstr; bintree *root; if (szexpress == NULL)  return NULL; root = (bintree *)malloc(sizeof(bintree)); if (*ptr == '+' || *ptr == '-')  {   root->op = 0;   root->level = getlevel(root->op);   root->fvalue = 0;   root->lchild = NULL;   root->rchild = NULL;  } else  {   while(*ptr)    {     if (isop(*ptr))      break;     *ptrnum++ = *ptr;     ptr++;    }   *ptrnum = '\0';   root->op = 0;   root->level = getlevel(root->op);   root->fvalue = atof(numstr);   root->lchild = NULL;   root->rchild = NULL;  } if (*ptr != '\0')  {   op = *ptr;   ptr++;   ptrnum = numstr;   while(*ptr)    {     if (isop(*ptr))      {       *ptrnum = '\0';       appendnode(&root, op, atof(numstr));       ptrnum = numstr;       op = *ptr;      }     else      *ptrnum++ = *ptr;     ptr++;    }   *ptrnum = '\0';   appendnode(&root, op, atof(numstr));  } return root;}