c++ - Change String Array to tolower -

in program have text file read array tokenizes each word. need way can compare words words found in binary tree. issue is... duplicates of words not formatted same way (one uppercase , 1 lowercase) , need them can found in binary tree.

so question is: how change whole array lowercase?

here tried far:

#include <iostream> #include "binary_searchtree.h" #include "node.h" #include <string> #include <fstream> #include <sstream>  using namespace std;  const int size = 100; string myarray[size];  int main() {      // first constructor used since empty     binary_searchtree<string> *tree = new binary_searchtree<string>();      string token, lines;     ifstream file("hashtags.txt");      while (getline(file, lines)){             tree -> insertnode(lines);      }      // convert strings in myarray all-lower     myarray = tolower(myarray);      // tokenize tweet array search     ifstream tweet1("exampletweet.txt");     if(tweet1.is_open())     {      while (getline(tweet1, token)){             for(int = 0; < size; ++i)             {             tweet1 >> myarray[i];             }      }     tweet1.close();  } 

with c++11 , later, can downcase array of strings this:

#include <algorithm> #include <cctype> #include <string>  std::string myarray[23];  // ...  (std::string & s : myarray)     std::transform(s.begin(), s.end(), s.begin(),                    [](unsigned char c) { return std::tolower(c); }); 

alternatively:

for (std::string & s : myarray)     std::for_each(s.begin(), s.end(), [](char & c) {         c = std::tolower(static_cast<unsigned char>(c)); }); 

or even:

for (std::string & s : myarray)     (char & c : s)         c = std::tolower(static_cast<unsigned char>(c)); 

if have c++98 support, use following loops:

for (std::size_t = 0; != 23; ++i) {     std::string & s = myarray[i];     (std::string::iterator = s.begin(), e = s.end(); != e; ++it)     {         *it = std::tolower(static_cast<unsigned char>(*it));     } } 

you idea.

don't forget convert character unsigned char, since that's std::tolower expects. (see this question discussion.) many c i/o functions expressed in terms of unsigned char-converted-to-int, since int big enough represent values of unsigned char plus additional out-of-band information, , char , unsigned char roundtrip convertible both ways layout-compatible.