這個題目比較坑在number和numbers上面。容易漏掉負號。容易漏掉小數點問題。pritnf輸出string還是會出錯。慎重選擇吧。

cin>>num[]也是合法的。

程式碼

//最初出錯在一個坑人的地方。num沒有初始化，本地通過了，oj沒有通過。果然厲害。以後一定記得要初始化啊。還有number 和numbers的問題。

#include<iostream>
#include<stdlib.h>
#include<string>
#include<sstream>
using namespace std;

int main(){
	char temp;
	string s;
	int n;
	char  a[100][100];
	int count=0,fcount=0,subcount=0;
	bool not_legal,after_float;
	cin>>n;
	
	int num=0;
	float number=0,legal;
	
	// while(cin>>s)
	for(int i=0;i!=n;i++)
	{
		cin>>s;
		not_legal =false;
		after_float=false;
		count=0;
		fcount=0;
		subcount=0;
			istringstream stream(s);
			while(stream>>temp){
				if(temp=='.'){
					after_float=true;
					count++;
				}
				else if(temp>'9'||temp<'0'){
					not_legal=true;
					if(temp=='-'&&subcount==0){
						subcount++;
						not_legal=false;
					}
				}
				
				if(after_float){
					fcount++;
				}
				
				if(count>1){
					not_legal=true;
				}
				
				if(fcount>3){
					not_legal=true;
				}
				
				
			}
			istringstream stm(s);
			stm>>legal;
			if(legal>1000||legal<-1000){
				not_legal=true;
			}
			
		if(not_legal){
			//printf("ERROR: %s is not a legal number\n",s);
			cout<<"ERROR: "<<s<<" is not a legal number"<<endl;
		}
		else{
			num++;
			// istringstream stream(s);
			// stream>>legal;
			number+=legal;
		}
	}
	if(num){
		if(num==1){
			printf("The average of %d number is %.2f\n",num,number/num);
		}
		else{
			printf("The average of %d numbers is %.2f\n",num,number/num);
		}
		// printf("The average of %d numbers is %.2f\n",num,number/num);
	}
	else{
		printf("The average of 0 numbers is Undefined\n");
	}
	
	
	return 0;
}