A1108. Finding Average

The basic task is simple: given N real numbers, you are supposed to calculate their average. But what makes it complicated is that some of the input numbers might not be legal. A "legal" input is a real number in [-1000, 1000] and is accurate up to no more than 2 decimal places. When you calculate the average, those illegal numbers must not be counted in.

Input Specification:

Each input file contains one test case. For each case, the first line gives a positive integer N (<=100). Then N numbers are given in the next line, separated by one space.

Output Specification:

For each illegal input number, print in a line "ERROR: X is not a legal number" where X is the input. Then finally print in a line the result: "The average of K numbers is Y" where K is the number of legal inputs and Y is their average, accurate to 2 decimal places. In case the average cannot be calculated, output "Undefined" instead of Y. In case K is only 1, output "The average of 1 number is Y" instead.

Sample Input 1:

7
5 -3.2 aaa 9999 2.3.4 7.123 2.35

Sample Output 1:

ERROR: aaa is not a legal number
ERROR: 9999 is not a legal number
ERROR: 2.3.4 is not a legal number
ERROR: 7.123 is not a legal number
The average of 3 numbers is 1.38

Sample Input 2:

2
aaa -9999

Sample Output 2:

ERROR: aaa is not a legal number
ERROR: -9999 is not a legal number
The average of 0 numbers is Undefined

 #include<cstdio>
 #include<iostream>
 #include<string.h>
 using namespace std;
 char num[];
 const double INF = 100000000.0;
 double prase_(char num[]){
     int len = strlen(num);
     int pos = -, cnt = ;
     int tag = ;
     for(int i = ; num[i] != '\0'; i++){
         if(!(num[i] >= '' && num[i] <= '' || num[i] == '.' || num[i] == '-')){
             return INF;
         }
         if(num[i] == '.')
             cnt++;
         if(cnt > )
             return INF;
     }
     if(num[] == '-')
         tag = ;
     for(pos = ; num[pos] != '.' && num[pos] != '\0'; pos++);
     int P = , ansL = , ansR = ;
     if(pos == '\0'){
         for(int i = len - ; i >= tag; i--){
             ansL += (num[i] - '') * P;
             P *= ;
         }
         if(tag == )
             return ansL * -1.0;
         else return ansL * 1.0;
     }else{
         if(len - pos -  > )
             return INF;
         P = ; ansL = ;
         for(int i = pos - ; i >= tag; i--){
             ansL += (num[i] - '') * P;
             P *= ;
         }
         P = ; ansR = ;
         for(int i = len - ; i > pos; i--){
             ansR += (num[i] - '') * P;
             P *= ;
         }
         double temp = ansR * 1.0;
         for(int i = ; i < len - pos - ; i++){
             temp *= 0.1;
         }
         if(tag == )
             return ((double)ansL + temp) * -1.0;
         else return (double)ansL + temp;
     }
 }
 int main(){
     int N, cnt = ;
     double sum = , temp = ;
     scanf("%d", &N);
     for(int i = ; i < N; i++){
         scanf("%s", num);
         temp = prase_(num);
         if(temp > 1000.0 || temp < -1000.0){
             printf("ERROR: %s is not a legal number\n", num);
         }else{
             sum += temp;
             cnt++;
         }
     }
     if(cnt > ){
         double prt = sum / (double)cnt;
         printf("The average of %d numbers is %.2f\n", cnt, prt);
     }else if (cnt == ){
         printf("The average of 0 numbers is Undefined\n");
     }else if(cnt == ){
         double prt = sum / (double)cnt;
         printf("The average of %d number is %.2f\n", cnt, prt);
     }
     cin >> N;
     return ;
 }