pat 1108 Finding Average（20 分）

1108 Finding Average（20 分）

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 <iostream>
 #include <algorithm>
 #include <cstdio>
 #include <cstring>
 #include <string>
 #include <map>
 #include <stack>
 #include <vector>
 #include <queue>
 #include <set>
 #define LL long long
 #define INF 0x3f3f3f3f
 using namespace std;
 const int MAX = 1e3;

 int n, cnt = ;
 double ans = 0.0;
 char s[MAX], notlegal[][MAX];

 bool my_is_ans()
 {
     int len = strlen(s), my_cnt = ;
 //    if (s[0] == '.' || s[len - 1] == '.') return false;
     for (int i = ; i < len; ++ i)
     {
         if (isalpha(s[i])) return false;
         if (s[i] == '.')
         {
             my_cnt ++;
             if (my_cnt >= ) return false;
             if (i <= len - ) return false;
         }
     }
     return true;
 }

 int main()
 {
 //    freopen("Date1.txt", "r", stdin);
     scanf("%d", &n);
     for (int i = ; i <= n; ++ i)
     {
         scanf("%s", &s);
         double d;

         if (!my_is_ans() || sscanf(s, "%lf", &d)!=  || d < - || d > )
         {
             strcpy(notlegal[cnt ++], s);
             continue;
         }
         ans += d;
     }

     for (int i = ; i < cnt; ++ i)
         printf("ERROR: %s is not a legal number\n", notlegal[i]);
     if (n - cnt == )
         printf("The average of 0 numbers is Undefined\n");
     else if (n - cnt == )
         printf("The average of 1 number is %.2lf\n", ans);
     else
         printf("The average of %d numbers is %.2lf\n", n - cnt, ans / (n - cnt));
     return ;
 }