c++ - const char * pointing to same memory location -

i trying break string integer , characters using below codes. in first section on immediate printing got right output later wrong.

int lottery::calcinvodds(string ruleconstraint){ const char * sorted; const char * unique; string temp; size_t pos;  temp = ruleconstraint;  pos = temp.find_first_of(" "); sorted = temp.substr(0,pos).c_str(); cout << temp << endl; cout << "s = " << sorted << endl;   temp = temp.substr(pos+1);  unique = temp.substr(0,pos).c_str();  cout << "u = " << unique << endl;  cout << "sorted = " << sorted[0] << " " << "unique = " << unique[0] << endl<<endl;  return 0; } 

output this:

t f s = t u = f sorted = f unique = f  f t s = f u = t sorted = t unique = t 

but after replacing const char * array char sorted[2] , temp.substr(0,pos).c_str(); *temp.substr(0,pos).c_str(), correct output displayed. reason of behaviour?

sorted = temp.substr(0,pos).c_str(); 

this isn't going work. temp.substr(0,pos) returns temporary string, .c_str() gets pointer contents, , after statement completes temporary string freed, making sorted point freed memory.

your best option not bother converting const char* , instead change sorted , unique strings. things work expect, because strings persist until function exits.

int lottery::calcinvodds(const string& ruleconstraint){     size_t pos = ruleconstraint.find_first_of(" ");     string sorted = ruleconstraint.substr(0, pos);     // above line rewritten as:     // string sorted(ruleconstraint, 0, pos);      cout << ruleconstraint << endl;     cout << "s = " << sorted << endl;      // -- not sure  want, it's code does.     #if 1     string unique = ruleconstraint.substr(pos + 1, pos);      // -- maybe meant     #else     size_t pos2 = ruleconstraint.find_first_of(" ", pos + 1);     string unique(ruleconstraint, pos + 1, pos2 - pos - 1);     #endif      cout << "u = " << unique << endl;      cout << "sorted = " << sorted[0] << " " << "unique = " << unique[0] << endl << endl;      return 0; }