下面这个“统计数字字母字符个数，还要输出所有数字字符之和”我真的做不来

#include<iostream>
using namespace std;

int main()
{
    char s[] = { 0 };
    int n;
    cin >> n;
    char c;
    int countA = 0;
    int counta = 0;
    int count1 = 0;
    int countoth = 0;
    int sum = 0;
    while (n--)
    {
        cin >> c;
        if (c>='A'&&c<='Z')
        {
            countA++;
        }
        else if (c >= 'a'&&c <= 'z')
        {
            counta++;
        }
        else if (c >= '0'&&c <= '9')
        {
            sum += c-48;
            count1++;
        }
        else
        {
            countoth++;
        }

    }
    cout << countA << " "<< counta << " "
        << count1 << " "<< countoth << endl;
    if (countoth!=0)
    {
        cout << sum << endl;
    }
    return 0;
}

#include<iostream>
using namespace std;
int main()
{
    char str[100];
    int i ;
    int  letterd,letterx,num ,other,sum=0;
    char c;
    cout<<"Please enter a string : ";
    cin>>str;
    letterd=letterx=num=other=0;
    for( i= 0;str[i]!='\0'; i++)
    {
       c=str[i];
        if((c>= 'A'&&c<='Z'))
            letterd ++;
        else if(c>='a'&& c<='z') 
            letterx ++;
        else if (c>='0' && c<='9')
            num++;
        else other ++;
    }
    sum=letterd+letterx+num+other;
    cout<<"letterd(大写)="<<letterd<<endl<<"letterx(小写)="<<letterx<<endl<<"num（数字）="<<num<<endl<<"other（其他）="<<other<<endl<<"sum（和）="<<sum;
    return 0;
}