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 = 0;
double ans = 0.0;
char s[MAX], notlegal[105][MAX];

bool my_is_ans()
{
    int len = strlen(s), my_cnt = 0;
//    if (s[0] == '.' || s[len - 1] == '.') return false;
    for (int i = 0; i < len; ++ i)
    {
        if (isalpha(s[i])) return false;
        if (s[i] == '.')
        {
            my_cnt ++;
            if (my_cnt >= 2) return false;
            if (i <= len - 4) return false;
        }
    }
    return true;
}

int main()
{
//    freopen("Date1.txt", "r", stdin);
    scanf("%d", &n);
    for (int i = 1; i <= n; ++ i)
    {
        scanf("%s", &s);
        double d;

        if (!my_is_ans() || sscanf(s, "%lf", &d)!= 1 || d < -1000 || d > 1000)
        {
            strcpy(notlegal[cnt ++], s);
            continue;
        }
        ans += d;
    }

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