post_no_bintree.c

用C语言实现一个简单数学计算器

#include <stdio.h>
#include <io.h>
#define LEN  255

float stack_num[LEN]; //操作数
char stack_op[LEN];  //操作符
int top_num, top_op;
char temp[2];
char poststr[LEN];
int postp;

init_stack()//初始化
{
  top_num=0;
  top_op=0;
}

int push_num(float num)//入
{
  if (top_num==LEN) return -1; //满
  stack_num[top_num]=num;
  top_num++;
  return 0;
}

int push_op(char op)//入
{
  if (top_op==LEN) return -1; //满
  stack_op[top_op]=op;
  top_op++;
  return 0;
}

float pop_num() //弹
{
  --top_num;
  return stack_num[top_num];
}

char pop_op() //弹
{
  --top_op;
  return stack_op[top_op];
}

int empty_num()//空？
{
  if (top_num==0) return 1; //空
  return 0;
}

int empty_op()//空？
{
  if (top_op==0) return 1; //空
  return 0;
}

int getnum(char ch)
{
  temp[0]=ch;
  temp[1]=0;
  return atoi(temp);
}

int comp(f_num)//比较优先级
{ char temp;
  if (empty_op()) return -1; //空
  temp=pop_op(); push_op(temp);
  switch (temp)
  {     case '+':
		case '-':{if (f_num>2) return 1;break;}
		case '*':
		case '/':{if (f_num>3) return 1;break;}
		case '(':{if (f_num>=1) return 1;break;}
        case '#':{return 1;}
		default:return -1;
  }
	return 0;
}

int compu() //计算
{ char op1;
  float num1,num2;
  if (empty_num()) {printf("  \nERROR INPUT");exit(0);}  num1=pop_num();  
  if (empty_num()) {printf("  \nERROR INPUT");exit(0);}  num2=pop_num();  
  if (empty_op())  {printf("  \nERROR INPUT");exit(0);}  op1=pop_op(); sprintf(postp,"%c",op1);postp++;
  switch (op1)
  { case '+':push_num(num1+num2);break;
	case '-':push_num(num2-num1);break;
	case '*':push_num(num1*num2);break;
	case '/':push_num(num2/num1);break;
	default:printf("  \nERROR INPUT");exit(0);
  }
  return 0;
}

main(int argc,char * argv[])
{ char ch;
  int flag;
  int pro;
  init_stack(); push_op('#');flag=1;memset(poststr,0,LEN);postp=poststr;
  if (argc!=2) {printf("请在命令行写出表达式！\n"); exit(0);}
  while ( (ch=argv[1][0]) != 0  )
  { 
   switch (ch)
	{case '1':
	case '2':
	case '3':
	case '4':
	case '5':
	case '6':
	case '7':
	case '8':
	case '9':
	case '0':{sprintf(postp,"%c",ch);postp++;push_num(getnum(ch));break;}
	case '+':
	case '-':{while ((pro=comp(2))==0) 
			  if (compu()==-1)
			  {printf("  \nERROR INPUT");exit(0);}
			  if (pro==-1){printf("  \nERROR INPUT");exit(0);}	
		      push_op(ch);
			  break;
			 }
	case '*':
	case '/':{while ((pro=comp(3))==0) 
			if (compu()==-1){printf("  \nERROR INPUT");exit(0);}
			  if (pro==-1){printf("  \nERROR INPUT");exit(0);}	
		      push_op(ch);
			  break;
			 }
	case '(':{push_op(ch);break;}
	case ')':{while (1)
			 {  if (empty_op()) {printf("  \nERROR INPUT");exit(0);} ch=pop_op();
				if (ch=='(') break;
				push_op(ch);if (compu()==-1){printf("  \nERROR INPUT");exit(0);}
			 }
		     break;}      
    case '#':{while (1)
			 {  if (empty_op()) {printf("  \nERROR INPUT");exit(0);} ch=pop_op();
				if (ch=='#') break;
				push_op(ch);if (compu()==-1){printf("  \nERROR INPUT");exit(0);}
			 }		      
			 break;}      
	default :printf("  \nERROR INPUT");exit(0);
	}
    
	argv[1]++;
	if ((argv[1][0]==0)&&(flag)) {flag=0;argv[1]--;argv[1][0]='#';}
  }//while
  if ((top_num!=1)||(top_op!=0)) {printf("  \nERROR INPUT");exit(0);}
  printf(" 后序表达式为：\n   %s",poststr);
  printf("\n 结果为：\n   %f\n",pop_num());
  return 0;
}