表达式求值

[cpp]
描述：思路很简单，优先级比较完的情况下，采用两个栈就可以完成了…… 
[cpp] 
#include <iostream> 
#include <cstdio> 
#include <cstring> 
#include "hanshu.h"  //头文件 
using namespace std; 
int flag;//下面会多次用到flag 
int num_value(char *s,char *str,double *num,int len,int i,int j);//计算实数值存入num中 
char get_precede(char a,char b);//比较两个字符优先级，获取优先级 
int calculate_num(char c,double *num,int j);//优先级比较大小后计算结果 
double solve_s(char *s ,char *str,double *num,int len);//处理函数，得出等式的结果 
int main() 
{ 
    freopen("a.txt","r",stdin); 
    double num[10010]; 
    char c,s[10010],str[10010]; 
    memset(s,0,sizeof(s)); 
    int left,right,len; 
    left=right=len=flag=0; 
    while(scanf("%c",&c)!=EOF)//单字符输入 
    { 
        if((c>='0'&&c<='9')||c=='.'||c=='('||c==')'||c=='+'||c=='-'||c=='*'||c=='/')//选择合适的字符输入 
        { 
            s[len++]=c; 
            if(c=='(') 
            { 
                if(!right)flag=1; 
                left++; 
            } 
            else if(c==')') 
            { 
                right++; 
                if(!left) flag=2; 
            } 
        } 
        if(c=='\n')//讨论几种不符合情况的输入 
        { 
            if(flag==2) printf("输入错误，首先出现了右括号！\n"); 
            else if(left>right) printf("左括号比右括号多!\n"); 
            else if(left<right) printf("右括号比左括号多!\n"); 
            else if(len<=0) printf("没有数据!\n"); 
            else 
            { 
                s[len++]='#'; 
                flag=0; 
                memset(str,0,sizeof(str)); 
                memset(num,0,sizeof(num)); 
                double x=solve_s(s,str,num,len); 
                if(flag) printf("出现零为除数\n"); 
                else printf("solve_s=%g\n",x); 
            } 
            memset(s,0,sizeof(s)); 
            flag=len=left=right=0; 
        } 
    } 
    return 0; 
} 
[cpp] 
//头文件 
[cpp] 
<pre name="code" class="cpp">#ifndef HANSHU_H_INCLUDED 
#define HANSHU_H_INCLUDED 
char str_operator[]= {'+','-','*','/','(',')','#'}; 
char str_precede[7][7]= 
{ 
    {'>','>','<','<','<','>','>'}, 
    {'>','>','<','<','<','>','>'}, 
    {'>','>','>','>','<','>','>'}, 
    {'>','>','>','>','<','>','>'}, 
    {'<','<','<','<','<','=',' '}, 
    {'>','>','>','>',' ','>','>'}, 
    {'<','<','<','<','<',' ','='} 
}; 
extern int flag; 
int num_value(char *s,char *str,double *num,int len,int i,int j) 
{ 
    int k,count(0),c(0); 
    for( k=i; k<len; k++) 
        if(s[k]>='0'&&s[k]<='9') 
        { 
            num[j]=num[j]*10+s[k]-'0'; 
            if(c) count++; 
        } 
        else if(s[k]=='.') c=1; 
        else break; 
    for( c=0; c<count; c++) 
        num[j]/=10; 
    if((i==1&&(s[i-1]=='+'||s[i-1]=='-'))||(i>=2&&(s[i-1]=='-'||s[i-1]=='+')&&s[i-2]=='(')) 
    { 
        flag=1; 
        if(s[i-1]=='-') num[j]=0-num[j]; 
    } 
    return k; 
} 
char get_precede(char a,char b) 
{ 
    int i,j; 
    for(int  k=0; k<7; k++) 
    { 
        if(a==str_operator[k]) i=k; 
        if(b==str_operator[k]) j=k; 
  &n

补充：软件开发 , C++ ,