计算字符串的长度

#include<iostream>
#include<string>
using namespace std;
int main() {
 string s;
 cin >> s;
 const char * p = s.c_str();
 int len = 0;
 while (*p++)
  len++;
 cout << "the length of string :" << len << endl;
 system("pause");
 return 0;
}