C++构建string迭代器输出string中字符的个数

include <iostream>
#include <string>
#include <algorithm>
using namespace std;
//计算字符个数
int count()
{
    static int count = 0;
    return count++;
}
 //遍历字符串
 void check(char _litter)
 {
    if(('a' <= _litter && _litter <= 'z') || ('A' <= _litter && _litter <= 'Z'))
        count();
 }
int main()
{
    //创建字符串sentence
    string sentence;
    cout << "enter a sentence: ";
    //从键盘输入字符串
    getline(cin, sentence);
    //构建string迭代器，分别sentence指向字符串的开头和结尾
    string::iterator str_ite_begin = sentence.begin();
    string::iterator str_ite_end = sentence.end();
    //用算法for_each遍历字符串，需引入头文件algorithm
    for_each(str_ite_begin, str_ite_end, check);
    //输出字符串中字符的个数
    cout << count() << endl;
    return 0;
}