1108. Finding Average (20) 字符串处理

时间限制
400 ms
内存限制
65536 kB
代码长度限制
16000 B
判题程序
Standard
作者
CHEN, Yue
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

非法数字形式样例中已经全部给出，注意只有一个合法数字的输出形式。

#include<iostream>#include<cstdio>#include<string>using namespace std;const int maxn = 101;bool Judge(string s,double &x){    int dot = 0,n1 = 0,n2 = 0;    int i = 0;    if(s[i]=='-') i++;    for(;i < s.size();i++){        if(s[i]=='.'){            dot++;            if(dot > 1) return 0;        } else if(s[i]>='0'&&s[i]<='9'){            if(dot) n2++;            else n1++;        } else return 0;    }    if(n2>2) return 0;    sscanf(s.c_str(),"%lf",&x);    if(x>=-1000&&x<=1000) return 1;    return 0;}       int main(){    int n,cnt = 0;    double x,ans = 0;    string s;    cin >> n;    for(int i = 0;i < n;i++){        cin >> s;        if(Judge(s,x)){            cnt++;            ans += x;        } else {            cout << "ERROR: " << s << " is not a legal number\n";        }    }    if(cnt==1){        printf("The average of 1 number is %.2f\n",ans);        return 0;    }    printf("The average of %d numbers is ",cnt);    if(cnt) printf("%.2f\n",ans/cnt);    else cout << "Undefined\n";    return 0;}