PAT (Advanced Level) Practice 1108 Finding Average (20分)

1.题目

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

2.代码

#include<iostream>
#include<string>
#include<cstdio>
#include<cstring>
#include<sstream>
#include<cstdlib>
using namespace std;
int main()
{
	int n;
	cin >> n;
	string temp;
	double t;
	int count = 0;
	double sum = 0;
	stringstream ss;
	for (int i = 0; i<n; i++)
	{
		cin >> temp;
		ss << temp;
		ss >> t;
		if (temp.find('.') != string::npos && (temp.length() - temp.find_last_of('.') - 1>2))
		{
			printf("ERROR: %s is not a legal number\n", temp.c_str()); 
			ss.str("");
			ss.clear();
			continue;
		}
		if (ss.eof()&&!ss.fail()&&t <= 1000 &&t >= -1000)
		{
			count++; sum += t;
		}
		else
			printf("ERROR: %s is not a legal number\n", temp.c_str());
		ss.str("");
		ss.clear();

	}
	if (count == 0)
		printf("The average of 0 numbers is Undefined\n");
	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;
}