c++ - How do I compare two different strings from two separate text files? -

i c++ rookie , not know doing wrong. assignment compare 2 different .txt files, each containing item along either number of items , price of item. trying print names , prices of items. lets using .txt file namesandquantity.txt includes:

3 books 4 pens 

and .txt file namesandprice.txt includes:

pens 3.45 books 19.55 

the code using prints out first match:

#include <iostream> #include <fstream> #include <cmath>  int main(){     string nameofitemp, nameofitemq;     double priceofitem;     int numberofitems;     ifstream indata;     ifstream indata2;     indata.open("namesandquantity.txt");     indata2.open("namesandprice.txt");     while (indata>>numberofitems>>nameofitemq){         while (indata2>>nameofitemp>>priceofitem){             if (nameofitemp==nameofitemq){                cout<<nameofitemq<<endl;                cout<<priceofitem;         }        } } 

this code prints out first line:

books 19.55 

what can better it?

it's because after first

while (indata2>>nameofitemp>>priceofitem){     if (nameofitemp==nameofitemq){         cout<<nameofitemq<<endl;         cout<<priceofitem;     }    

executes, indata2 reaches end , not read more. solution move open function while loop:

while (indata>>numberofitems>>nameofitemq){     indata2.open("namesandprice.txt");     while (indata2>>nameofitemp>>priceofitem){         if (nameofitemp==nameofitemq){            cout<<nameofitemq<<endl;            cout<<priceofitem;     }     indata2.close();   } 

however, not best approach. you'd better use map avoid nested loops. map array except can choose use string index:

#include <iostream> #include <fstream> #include <string> #include <map>  using namespace std;  int main() {     // same before     int numberofitems;     string nameofitem;     double price;      // create map, using string index , int value.     map<string, int> items;      ifstream indata("namesandquantity.txt");     ifstream indata2("namesandprice.txt");      while (indata >> numberofitems >> nameofitem)       items[nameofitem] = numberofitems;      while (indata2 >> nameofitem >> price)       cout << nameofitem << " "            << items[nameofitem] << " " << price << endl;      indata.close();     indata2.close();      return 0; } 

output

pens 4 3.45 books 3 19.55