1108 Finding Average

#include<bits/stdc++.h>
using namespace std;
bool judge(string a){
	int ansnot=0;int flag=0;int ansnotafter=0;
	for(int i=0;i<a.length();i++){
		if(a[i]<='z'&&a[i]>='a') return false;
		if(flag==1) ansnotafter++;
		if(a[i]=='.'){
			flag=1;
			ansnot++;
		}
		if(ansnot>1) return false;
		if(ansnotafter>2) return false;
	}
	return true;
}
double getnum(string a){
	int flag=0;
	if(a[0]=='-'){
		flag=1;a=a.substr(1,a.length());
	}
	double ans=0;int notflag=0;int j=1;
	for(int i=0;i<a.length();i++){
		if(notflag==1){
			ans=ans+(a[i]-'0')*(pow(10,(0-j)));j++;
		}else{
			if(a[i]<='9'&&a[i]>='0')
			ans=ans*10+(a[i]-'0');
		}
		if(a[i]=='.'){
			notflag=1;continue;
		}
	}
	if(flag==1) return 0-ans;
	else return ans;
}
int main()
{
	freopen("in.txt","r",stdin);
	int n;cin>>n;double ans=0;int cnt=0;
	for(int i=0;i<n;i++){
		string temp;cin>>temp;
		if(judge(temp)==true){
			if(getnum(temp)>1000||getnum(temp)<-1000){
				cout<<"ERROR: "<<temp<<" is not a legal number"<<endl;cnt++;
			}else{
				ans+=getnum(temp);
			}
		}else{
			cout<<"ERROR: "<<temp<<" is not a legal number"<<endl;cnt++;
		}
	}
	if(cnt==n){
		cout<<"The average of 0 numbers is Undefined"<<endl;
	}else if(cnt==n-1){
		cout<<"The average of 1 number is ";
		printf("%.2lf\n",ans);
	}else{
		cout<<"The average of "<<n-cnt<<" numbers is ";
		printf("%.2lf\n",ans/((n-cnt)*1.0));
	}
}
 

虽然情况有很多种，但实际上只要考虑题中的几个情况并加以限制就可以了...