stringstream快速实现String和int之间的转换

需要包含头文件”sstream”

 #include <iostream>
 #include <string>
 #include <sstream>
 using namespace std;
 int string2int(string str){
     int num;
     stringstream sstream;
     sstream << str;
     sstream >> num;
     return num;
 }
 string int2string(int num){
     string re;
     stringstream sstream;
     sstream << num;
     return sstream.str();
 }