题目：https://pintia.cn/problem-sets/994805260223102976/problems/994805272659214336
参考：https://www.liuchuo.net/archives/617

注意点

这题主要利用了sscanf和sprintf，如下

  1. sscanf(a, "%lf", &temp);//把a输入进temp中
  2. sprintf(b, "%.2f", temp);//把temp的东西打印到b里

代码

  1. #include<iostream>
  2. #include<cstdio>
  3. #include<cstring>
  4. using namespace std;
  5. int main(){
  6.     int n, cnt = 0;
  7.     char a[50], b[50];
  8.     double temp, sum = 0.0;
  9.     cin >> n;
  10.     for(int i = 0; i < n; i++){
  11.         scanf("%s", a);
  12.         sscanf(a, "%lf", &temp);
  13.         sprintf(b, "%.2f", temp);
  14.         int flag = 0;
  15.         for(int j = 0; j < strlen(a); j++)
  16.             if(a[j] != b[j]) flag = 1;
  17.         if(flag || temp < -1000 || temp > 1000){
  18.             printf("ERROR: %s is not a legal number\n", a);
  19.             continue;
  20.         } else {
  21.             sum += temp;
  22.             cnt++;
  23.         }
  24.     }
  25.     if(cnt == 1){
  26.         printf("The average of 1 number is %.2f", sum);
  27.     } else if(cnt > 1)
  28.         printf("The average of %d numbers is %.2f", cnt, sum / cnt);
  29.     else
  30.         printf("The average of 0 numbers is Undefined");
  31.     return 0;
  32. }