1054 求平均值 （20 分）

#include <iostream>
#include<string>
#include<math.h>
#include<ctype.h>
#include<stdlib.h>
using namespace std;
string str[100];
int n;
bool check(string s) {
	int i = 0;
	if (s[i] == '-')i++;
	for (;s[i] && s[i] != '.';i++) {
		if (!isdigit(s[i])) {//判断字符是否为数字字符
			return false;
		}
	}
	if (s[i] == '.') {
		for (int j = i + 1;s[j];j++) {
			if (!isdigit(s[j]) || j - i > 2) {
				return false;
			}
		}
	}
	double x = fabs(atof(&s[0]));//将字符串转换成浮点数
	if (x > 1000) {
		return false;
	}
	return true;
}
void solve() {
	int count = 0;
	double sum = 0;
	for (int i = 0;i < n;i++) {
		if (check(str[i])) {
			count++;
			sum += atof(&str[i][0]);
		}
		else {
			cout << "ERROR: " << str[i] << " is not a legal number" << endl;
		}
	}
	if (count == 0) {
		cout << "The average of 0 numbers is Undefined" << endl;
	}
	else if (count == 1) {
		printf("The average of 1 number is %.2lf
", sum);
	}
	else {
		double y = sum / (double)count;
		printf("The average of %d numbers is %.2lf
", count, y);
	}

}
int main()
{
	cin >> n;
	for (int i = 0;i < n;i++) {
		cin >> str[i];
	}
	solve();
	return 0;
}

参考博客：https://blog.csdn.net/hy971216/article/details/80653566