[PAT-A] 1108 Finding Average

Java

import java.util.ArrayList;
import java.util.List;
import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        double[] cal = new double[100];
        List<String> invalidStrs = new ArrayList<>();

        int cnt = 0;
        int num = Integer.parseInt(sc.nextLine());

        String[] lines = sc.nextLine().trim().split(" ");

        for (String line : lines) {
            if (isNormal(line)) {
                cal[cnt++] = Double.parseDouble(line);
            } else {
                invalidStrs.add(line);
            }
        }

        for (String str : invalidStrs) {
            System.out.println("ERROR: " + str + " is not a legal number");
        }

        double sum = 0, res;
        for (double v : cal) {
            sum += v;
        }
        if (cnt == 1) {
            res = sum / cnt;
            System.out.printf("The average of %d number is %.2f", cnt, res);
        } else if (cnt > 1) {
            res = sum / cnt;
            System.out.printf("The average of %d numbers is %.2f", cnt, res);
        } else {
            System.out.println("The average of 0 numbers is Undefined");
        }
    }

    public static boolean isNormal(String str) {
        try {
            if (Double.parseDouble(str) <= 1000 && Double.parseDouble(str) >= -1000) {
                return pointLegal(str);
            } else {
                return false;
            }
        } catch (Exception e) {
            return false;
        }
    }

    public static boolean pointLegal(String str) {
        char[] chars = str.toCharArray();
        int indexOfPoint;
        int length = str.length();

        if (str.contains(".")) {
            indexOfPoint = str.indexOf(".");
            if (indexOfPoint == 0) {
                return false;
            }
            if (indexOfPoint > 0 && chars[indexOfPoint - 1] == '-') {
                return false;
            }
            return length - indexOfPoint <= 3;
        }
        return true;
    }
}

C++

#include <iostream>
#include <cstring>
#include <cmath>
#include <algorithm>

using namespace std;

int n, cnt = 0;
double sum = 0;

bool check(string s) {
    if (s[0] != '-' && !isdigit(s[0])) return false;
    if (s[0] == '-' && s.size() == 1) return false;

    int dotnum = 0, len = 0;
    for (int i = 1; i < s.size(); ++i) {
        if (isdigit(s[i])) {
            if (dotnum) len++;
        } else if (s[i] == '.') {
            dotnum++;
            if (dotnum > 1) return false;
        } else return false;
    }

    if (len > 2) return false;

    double a = stod(s);
    if (a < -1000 || a > 1000) return false;
    return true;
}

int main() {
    scanf("%d", &n);

    string s;
    while (n--) {
        cin >> s;

        if (check(s)) {
            sum += stod(s);
            cnt++;
        } else printf("ERROR: %s is not a legal number\n", s.c_str());
    }

    if (!cnt) printf("The average of 0 numbers is Undefined\n");
    else if (cnt == 1) printf("The average of 1 number is %.2f\n", sum);
    else printf("The average of %d numbers is %.2f\n", cnt, sum * 1.0 / cnt);

    return 0;
}