# Realization of Simple Code in PAT 1054 Average C Language

The basic requirement of this question is very simple: Given N real numbers, calculate their average value. But complex is that some input data may be illegal. A "legitimate" input is a real number in the interval [1000,1000] and is at most accurate to two decimal places. When you calculate the average, you can't count the illegal data.

### Input format:

Input the first line to give a positive integer N (< 100). The next line gives N real numbers separated by a space.

### Output format:

For each illegal input, ERROR: X is not a legal number, where X is the input. Finally, The average of K numbers is Y, where K is the number of legitimate inputs and Y is their average value, accurate to two decimal places. If the average cannot be calculated, replace Y with Undefined. If K is 1, The average of 1 number is Y.

### Input Sample 1:

```7
5 -3.2 aaa 9999 2.3.4 7.123 2.35
```

### Output Sample 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
```

### Output Sample 2:

```ERROR: aaa is not a legal number
ERROR: -9999 is not a legal number
The average of 0 numbers is Undefined```
```#include<stdio.h>
#include<stdlib.h>

int main()
{
int N = 0;
scanf("%d",&N);
char str = {};	//Original string
char dest = {}; //Keep two decimal strings
double num = 0;
int flag = 0;		//Is the record illegal?
double Y = 0;
int K = 0;
for(int i = 0 ; i < N ; i++)
{
flag = 0;
scanf("%s",str);
sscanf(str,"%lf",&num);
sprintf(dest,"%.2f",num);
for(int i = 0 ;'\0' != str[i];i++)
{
if(str[i] != dest[i])
{
flag = 1;
break;
}
}
if(1 == flag || num < -1000 || num > 1000)
printf("ERROR: %s is not a legal number\n",str);
else
{
Y += num;
K++;
}
}
if(0 == K)
printf("The average of 0 numbers is Undefined\n");
else if(1 == K)
printf("The average of 1 number is %.2f\n",Y);
else
printf("The average of %d numbers is %.2lf\n",K,Y/K);
return 0;
}
```

Added by dbakker on Thu, 03 Oct 2019 17:54:12 +0300