1108. Finding Average (20)
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 思路
逻辑题，注意处理下负数的情况，其余按题目要求设置好if语句的条件就行。 代码
#include<iostream>
#include<iomanip>
#include<string>
using namespace std; bool islegal(string s)
{
int len = s.size();
int dotcount = ;
int i = ;
if(s[i] == '-')
{
if(i + == len)
return false;
i++;
}
for(;i < len;i++)
{
if(s[i] == '.')
{
dotcount++;
if(dotcount > )
return false;
if(len - - i > )
return false;
}
else if(s[i] < '' || s[i] > '')
return false;
}
double num = stod(s);
if(num < - || num > )
return false;
return true;
} int main()
{
int N;
while(cin >> N)
{
string str;
double sum = ;
int cnt = ;
for(int i = ;i < N;i++)
{
cin >> str;
if(islegal(str))
{
cnt++;
sum += stod(str);
}
else
{
cout << "ERROR: " << str << " is not a legal number" << endl;
}
}
if(cnt == )
cout << "The average of "<< cnt <<" numbers is Undefined" << endl;
else if(cnt == )
cout << "The average of 1 number is " << fixed << setprecision() << sum << endl;
else
cout << "The average of "<< cnt <<" numbers is "<< fixed << setprecision() << sum/cnt << endl;
}
}