二叉树运用

#include<stdlib.h>
#include<stdio.h>
#include<string.h>
#include<ctype.h>
#define MAX_LEN 5
typedef struct node{
  char optr;
  int data;
  struct node* lchild;
  struct node* rchild;
}BTNode;
BTNode * getNode(char *str,int &pos){
 BTNode *createTree(char *str,int &pos);
 BTNode *p=new BTNode;
 char ch=str[0];
 if(isdigit(ch)){
  int i=0;
  char data[MAX_LEN];
  while(isdigit(ch=str[i]))
   data[i++]=ch;
  p->data=atoi(data);
  pos+=i;
 }
 else if(ch=='+'||ch=='-'||ch=='*'||ch=='/'){
  p->optr=ch;
  pos+=1;
 }
 else if(ch=')'){
  pos+=1;
  return NULL;
 }
 else if(ch=='')
  return NULL;
 return p;
}
 int getPriority(char optr){
  switch(optr){
   case'+':
   case'/':
    return 1;
   case'*':
   case'/':
    return 2;
  }
  return 0;
 }
 BTNode *createTree(char *str,int &pos){
  int pos1=0;
  BTNode *lchild=getNode(str+pos1,pos1);
  BTNode *root=getNode(str+pos1,pos1);
  BTNode *rchild=getNode(str+pos1,pos1);
  root->lchild=lchild;
  root->rchild=rchild;
  BTNode *node;
  while((node=getNode(str+pos1,pos1))){
   if(getPriority(root->optr)>getPriority(node->optr)){
    node->lchild=root;
    node->rchild=getNode(str+pos1,pos1);
    root=node;
   }
   else{
    node->lchild=root->rchild;
    root->rchild=node;
    node->rchild=getNode(str+pos1,pos1);
   }
  }
  pos+=pos1;
  return root;
 }
int result(BTNode *b){
 int n1,n2;
 switch(b->optr){
  case'+':
   n1=result(b->lchild);
   n2=result(b->rchild);
   b->data=n1+n2;
   break;
  case'-':
   n1=result(b->lchild);
   n2=result(b->rchild);
   b->data=n1-n2;
   break;
  case'*':
   n1=result(b->lchild);
   n2=result(b->rchild);
   b->data=n1*n2;
   break;
  case'/':
   n1=result(b->lchild);
   n2=result(b->rchild);
   b->data=n1/n2;
   break;
  default:
   return b->data;
 }
 return b->data;
}
int main(){
 BTNode*b=NULL,*q=NULL;
 char str[100];
 printf("Please enter SQC£º");
 scanf("%s",str);
 int n=0,i=0;
 while(str[i++]!='')
  n++;
 int pos=0;
 b=createTree(str,pos);
 printf("ASM:%d
",result(b));
}