PAT甲级——A1108 Finding Average【20】

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 [−] 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 (≤). 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 <vector>
using namespace std;
#define inf 1000
double sum = 0.0, number;
int n, nums = 0;
int main()
{
    cin >> n;
    char str1[100], str2[100];
    while (n--)
    {
        cin >> str1;
        bool flag = true;
        sscanf(str1, "%lf", &number);//将字符转换为浮点数值
        sprintf(str2, "%0.2f", number);//按要求输出
        for (int i = 0; str1[i] != ''&& flag; ++i)
            if (str1[i] != str2[i])
                flag = false;
        if (!flag || number<-inf || number>inf)
            cout << "ERROR: " << str1 << " is not a legal number" << endl;
        else
        {
            nums++;
            sum += number;
        }
    }
    cout << "The average of " << nums << (nums == 1 ? " number is " : " numbers is ");
    if (nums == 0)
        cout << "Undefined" << endl;
    else
        printf("%0.2f
", sum / nums);
    return 0;
}