PAT A1108. Finding Average (20/17)

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<cstdio>
#include<algorithm>
#include<cstring>
#include<string>
#include<iostream>
const int Max = 1000;
using namespace std;
int n;
string S[Max];
double num[Max];
int ins=0;
bool IsTrue(string s)
{
	if(s[0]=='-')
	{
		if(s[1]>='0'&&s[1]<='9')
			{
				int flag=0,k=-1;
				for(int i=1;i<s.size();i++)
				{
					if(!(s[i]>='0'&&s[i]<='9'||s[i]=='.'))
					{
						return false;
					}
					if(s[i]=='.')
					{
						if(flag==0)
						{
							k=i;//找到.的位置
						}
						flag++;
					}
					if(flag>=2) 
					{
						return false;
					}
				}
				if(k==-1)//不是小数
				{
					double ans=0;
					for(int i=1;i<s.size();i++)
					{
						ans=ans*10+(s[i]-'0');
					}
					if(ans>1000)
						return false;
					else 
					{
						num[ins++]=-1*ans;
						return true;
					}
				}
				else 
				{
					if(s.size()-k-1>=3)
					{
						return false;
					}
					else 
					{
						double ans1=0,ans2=0;
					    for(int i=1;i<k;i++)
					    {
						    ans1=ans1*10+(s[i]-'0');
					    }
						for(int i=k+1;i<s.size();i++)
						{
							ans2=ans2*10+(s[i]-'0');
						}
						if(s.size()-k-1==2) ans2=ans2/100;
						else ans2=ans2/10;
						ans1=ans1+ans2;
						num[ins++]=-1*ans1;
						return true;
					}
				}
			}
			
	    else return false;
	}

	
	else //正数
	{

			if(s[0]>='0'&&s[0]<='9')
			{
				int flag=0,k=-1;
				for(int i=0;i<s.size();i++)
				{
					if(!(s[i]>='0'&&s[i]<='9'||s[i]=='.'))
					{
						return false;
					}
					if(s[i]=='.')
					{
						if(flag==0)
						{
							k=i;//找到.的位置
						}
						flag++;
					}
					if(flag>=2) 
					{
						return false;
					}
				}
				if(k==-1)//不是小数
				{
					double ans=0;
					for(int i=0;i<s.size();i++)
					{
						ans=ans*10+(s[i]-'0');
					}
					if(ans>1000)
						return false;
					else 
					{
						num[ins++]=ans;
						return true;
					}
				}
				else 
				{
					if(s.size()-k-1>=3)
					{
						return false;
					}
					else 
					{
						double ans1=0,ans2=0;
					    for(int i=0;i<k;i++)
					    {
						    ans1=ans1*10+(s[i]-'0');
					    }
						for(int i=k+1;i<s.size();i++)
						{
							ans2=ans2*10+(s[i]-'0');
						}
						if(s.size()-k-1==2) ans2=ans2/100;
						else ans2=ans2/10;
						ans1=ans1+ans2;
						num[ins++]=ans1;
						return true;
					}
				}
			}
			
	    else return false;
	}
}
int main()
{
	scanf("%d",&n);
	for(int i=0;i<n;i++)
	{
		getchar();
		cin>>S[i]; 
	}
	int temp=0;
	for(int i=0;i<n;i++)
	{
		if(IsTrue(S[i])==false)
		{
			cout<<"ERROR: "<<S[i]<<" is not a legal number"<<endl;
		}
	}
	if(ins==0)
	{
		cout<<"The average of 0 numbers is Undefined"<<endl;
	}
	else 
	{
		double mm=0;
		for(int i=0;i<ins;i++)
		{
			mm+=num[i];
			//cout<<num[i]<<endl;
		}
		mm=mm/ins;
		if(ins!=1)
		printf("The average of %d numbers is %.2f",ins,mm);
		else printf("The average of %d number is %.2f",ins,mm);
	}
	system("pause");
	return 0;
}