1. string转int

string str;

int Num = atoi(str.c_str());

2.string转char*

string s = "how";

const char *c = s.c_str(); //或s.data();

3.in转string

#include <sstream>

string numToStr(int numn){

stringstream ss;

ss << numn;

string s2;

ss>>s2;

return s2;

}