atof(str)字符串转换浮点数

1 #include
     
       2 using namespace std; 3 bool isLegal(char *s){ 4     int i = 0; 5     if(s[0]=='-'){ 6         i++; 7     } 8     for(;s[i]&&s[i]!='.';i++){ 9         if(!isdigit(s[i])){10             return false;11         }12     }13     if(s[i]=='.'){14         for(int j=i+1;s[j];j++){15             if(!isdigit(s[j])||j-i>2){16                 return false;17             }18         }19     }20     double a = fabs(atof(s));21     if(a>1000.0){22         return false;23     }24     return true;25 }26 int main(){27     int n,nums = 0;28     double sum;29     char *x;30     x=(char *)malloc(sizeof(char));31     cin>>n;32     for(int i = 0; i < n; i++){33         scanf("%s", x);34         if(isLegal(x)){35             nums++;36             sum += atof(x);37         }else{38             printf("ERROR: %s is not a legal number\n", x);39         }    40     }41     if(nums){42         if(nums==1){43             printf("The average of 1 number is %.2lf\n",sum);44         }else{45             printf("The average of %d numbers is %.2lf\n",nums,sum/nums);46         }47     }else{48         printf("The average of 0 numbers is Undefined\n");49     }50     return 0;51 }