题解 | #使用字符函数统计字符串中各类型字符的个数#

#include <iostream>
#include <string>

using namespace std;

int main() {

    string str;
    getline(cin, str);

    int whitespace = 0;
    int digits = 0;
    int chars = 0;
    int others = 0;

    // write your code here......
    for (auto a: str)
    {
        if (a >= '0' && a <= '9')
            ++digits;
        else if ((a >= 'a' && a <='z') || (a >= 'A' && a <= 'Z'))
            ++chars;
        else if (a == ' ')
            ++whitespace;
        else
            ++others; 
    }

    cout << "chars : " << chars
        << " whitespace : " << whitespace
        << " digits : " << digits
        << " others : " << others << endl;

    return 0;
}

使用范围for循环。范围for循环等价于：

char* str_point = &str[0];
while(*str_point != '\0')
{
        if (*str_point >= '0' && *str_point <= '9')
            ++digits;
        else if ((*str_point >= 'a' && *str_point <='z') || (*str_point >= 'A' && *str_point <= 'Z'))
            ++chars;
        else if (*str_point == ' ')
            ++whitespace;
        else
            ++others;
        str_point++;
}