中缀表达式转后缀表达式并求值

#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include<math.h>
char c1[101],c2[101],c3[101];
float a[101];
int main(){
	int i,j,k,m,n;
    int top=0,v=-1,u=0;
	gets(c1);
    k=strlen(c1);
    for(i=0;i<k;i++){
	  switch(c1[i]){
	  case '(':c2[++top]=c1[i];break;
	  case '+':
	  case '-':while(top>0 && c2[top]!='('){
				 c3[++v]=c2[top];
				 c3[++v]=' ';
				 top--;
			   }
			   c2[++top]=c1[i];
			   break;
	  case '*':
	  case '/':while(top>0 && c2[top]!='(' && c2[top]!='+' && c2[top]!='-'){
	             c3[++v]=c2[top];
	             c3[++v]=' ';
	             top--;
	           }
	           c2[++top]=c1[i];
	           break;
	  case ')':while(c2[top]!='('){
	             c3[++v]=c2[top];
	             c3[++v]=' ';
	             top--;
			   }
			   top--;
			   break;
	  default:
	  	   c3[++v]=c1[i];
	  	   if(c1[i+1]>'9' || c1[i+1]<'0')
	  	     c3[++v]=' ';
	  	   break;
	  }
	}
	while(top>0 && c2[top]!='('){
	  c3[++v]=c2[top];
	  c3[++v]=' ';
	  top--;
	  }
	puts(c3);
	top=0;
	float sum;
	k=strlen(c3);
	for(i=0;i<k;i++){
        if(c3[i]==' ');
        else if(c3[i]=='+'){sum=a[top-1]+a[top];a[--top]=sum;}
        else if(c3[i]=='-'){sum=a[top-1]-a[top];a[--top]=sum;}
        else if(c3[i]=='*'){sum=a[top-1]*a[top];a[--top]=sum;}
        else if(c3[i]=='/'){sum=a[top-1]/a[top];a[--top]=sum;}
        else{
          int m=0;
            while(c3[i]>='0' && c3[i]<='9'){
              m=10*m+c3[i]-'0';
              i++;
            }
            a[++top]=m;
        }
    }
	printf("%.8f
",a[top]);
	return 0;
}