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

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

## 分析

#define _CRT_SECURE_NO_WARNINGS
#include<iostream>
#include<string>
#include<cstring>
#include<cmath>

using namespace std;

int main()
{
int n, cnt = 0;
char inputString[30], buff[30];
scanf("%d", &n);
double num = 0, sum = 0;
for (int i = 0; i < n; i++) {
scanf("%s", inputString);
sscanf(inputString, "%lf", &num);
sprintf(buff, "%.2f", num);
bool flag = false;
for (int j = 0; j < strlen(inputString); j++)
if (inputString[j] != buff[j]) {
flag = true;
break;
}
if (flag || num < -1000 || num>1000) {
printf("ERROR: %s is not a legal number\n", inputString);
continue;
}
else {
sum += num;
cnt++;
}
}
if (cnt == 1) printf("The average of 1 number is %.2f", sum);
else if (cnt) printf("The average of %d numbers is %.2f", cnt, sum / cnt);
else printf("The average of 0 numbers is Undefined");
return 0;
}


int main()
{
int n, count = 0, dec = 1;
bool dotFlag = false;
bool negFlag = false;
bool invalid = false;
double sum = 0;
string in;
cin >> n;
for (int i = 0; i < n; i++) {
double dig = 0;
cin >> in;
// 负数
for (auto j = 0; j < in.size(); j++) {
if ('9' >= in[j] && in[j] >= '0') {
if (!dotFlag) dig = 10.0 * dig + (in[j] - '0');
else if (dec <= 2) dig = dig + (in[j] - '0') / pow(10, dec++);
else {
invalid = true;
break;
}
}
else if (in[j] == '-' && j == 0) negFlag = true;
else if (!dotFlag && in[j] == '.' && j >= 1) dotFlag = true;
else {
invalid = true;
break;
}
}
if (dig > 1000 || dig < -1000) invalid = true;
if (invalid) printf("ERROR: %s is not a legal number\n", in.c_str());
else {
if (negFlag) dig = -dig;
sum += dig;
count++;
}
invalid = false;
negFlag = false;
dec = 1;
dotFlag = false;
}
if (count == 0) printf("The average of 0 numbers is Undefined");
else if (count == 1) printf("The average of 1 number is %.2f", sum);
else printf("The average of %d numbers is %.2f", count, sum / count);
return 0;
}