2. C++ 统计字符串中英文字母、空格、数字和其它字符的个数

输入一行字符，分别统计其中字母、空格、数字和其他字符的个数。
 1 //
// Created by Green on 2021/6/9.
//
#include <iostream>

using namespace std;
int letters, digit, space, others;

int main(void) {
    cout << "please input some characters" << endl;
    int c;
    while ((c = getchar()) != '\n') {
        if (c >= 'a' && c <= 'z' || c >= 'A' && c <= 'Z') {
            letters++;
        } else if (c == 32) {
            space++;
        } else if (c >= '0' && c <= '9') {
            digit++;
        } else {
            others++;
        }
    }
    cout << "letters: " << letters << endl
         << "digit: " << digit << endl
         << "space: " << space << endl
         << "others: " << others << endl;
    return 0;
}