PAT 甲 1108 Finding Average

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
题意:
与乙1054相同
给定 N 个实数，计算它们的平均值。但复杂的是有些输入数据可能是非法的。一个“合法”的输入是 [−1000,1000] 区间内的实数，并且最多精确到小数点后 2 位。当你计算平均值的时候，不能把那些非法的数据算在内。
输入第一行给出正整数 N（≤100）。随后一行给出 N 个实数，数字间以一个空格分隔。
对每个非法输入，在一行中输出 ERROR: X is not a legal number，其中 X 是输入。最后在一行中输出结果：The average of K numbers is Y，其中 K 是合法输入的个数，Y 是它们的平均值，精确到小数点后 2 位。如果平均值无法计算，则用 Undefined 替换 Y。如果 K 为 1，则输出 The average of 1 number is Y
思路:
用字符数组存取每一个数，然后用sscanf转为double型浮点数，然后再用sprintf将该浮点数保留两位小数转为字符数组，比较两字符数组是否相同
C++代码:

#include<iostream>
#include<cstdio>
#include<cstring>
using namespace std;
int main(){
	int n;
	cin>>n;
	double sum=0;
	int count=0;
	char str1[101],str2[101];
	for(int i=0;i<n;i++){
		scanf("%s",str1);
		double d;
		sscanf(str1,"%lf",&d);
		sprintf(str2,"%.2lf",d);
		bool flag=true;
		for(int j=0;j<strlen(str1);j++){
			if(str1[j]!=str2[j]){
				flag=false;
				break;
			}
		}
		if(flag==false){
			cout<<"ERROR: "<<str1<<" is not a legal number"<<endl;
		}
		else if(d>1000||d<-1000){
			cout<<"ERROR: "<<str1<<" is not a legal number"<<endl;
		}
		else{
			count++;
			sum+=d;
		}
	}
	if(count==0){
		printf("The average of %d numbers is Undefined",count);
	}
	else if(count==1){
		printf("The average of %d number is %.2f",count,sum/count);
	}
	else{
		printf("The average of %d numbers is %.2f",count,sum/count);
	}
	
	return 0;
	
	
	
	
}