Re: Strings, Arrays, c++ and java

On Tue, 25 Mar 2008 17:19:34 -0700 (PDT), zionz <zionztp@gmail.com>
wrote:


Let me post the whole program so you can test both. You version
doesn't work

=== C++===
#include <iostream>
#include <cstdlib>
#include <ctime>
#include <string>

using namespace std;

const int len = 50000000;
void getRandomString( std::string& s, size_t len);
void randomString( std::string& s);

int main( int argc, char *argv[])
{
  if (argc < 2) { cout << "Fool enter text to search"; exit(0);}

   string s;
   
   string toSearch = argv[1];
   
clock_t start=clock();
   randomString (s);
  //getRandomString(s, len); version by Ian
clock_t endt=clock();

   int found = s.find (toSearch);
   int count = 0;
   while (found!=string::npos)
   {
      count++;
      found=s.find(toSearch,found+1);
   }
   
   std::cout <<"Number of " << toSearch << ": " << count << "\n";
  std::cout <<"Time: " <<
          double(endt-start)/CLOCKS_PER_SEC * 1000 << " ms\n";
}

/*
   //my version
   void getRandomString( std::string& s, size_t len )
   {
    srand((unsigned)std::time(0));
       
        std::string cr( len, '\0' );
        for( int i = 0 ; i < len ; ++i )
        {
          int iNumber;
          iNumber = rand() % 26 + 97;
         cr[i] = (char) iNumber;
        }

       s.swap( cr );
   }

*/

//version by zionz
void randomString(std::string &s)
{
    char cr[len];
    int n;
    unsigned char tn[4];
    srand((unsigned)std::time(0));
    for( int i = 0 ; i < len; i+=4 ){
        n = rand();
        memcpy(tn, &n, 4);
        s+= (char) (tn[0] % 26 + 97);
        s+= (char) (tn[1] % 26 + 97);
        s+= (char) (tn[2] % 26 + 97);
        s+= (char) (tn[3] % 26 + 97);
    }
}

//version by Ian Collins
void getRandomString( std::string& s, size_t len )
{
  srand(std::time(0));

  std::string cr( len, '\0' );

  // The following code is based on the requirement that RAND_MAX
  // shall be at least 32767.
  //
  const size_t byThree = (len/3)*3;

  size_t i(0);

  while( i < byThree )
  {
    const int iNumber( rand() );

    cr[i++] = iNumber % 26 + 97;
    cr[i++] = (iNumber>>5) % 26 + 97;
    cr[i++] = (iNumber>>10) % 26 + 97;
  }

  while( i < len )
  {
    const int iNumber( rand() );

    cr[i++] = iNumber % 26 + 97;
  }

  s.swap( cr );
}

===Java===

import java.util.*;

public class Find{
 
 public static void main(String[] arg)
  {
   if (arg == null)
   {
 System.out.println("Fool! Enter text on command line to search");
   System.exit(-1);
   }
  
   final int len = 50000000;
   String toSearch = arg[0];
  
     //create a string with 50 million chars from a-z
     
         long start = System.currentTimeMillis();
     String s = randomString(len);
         long end = System.currentTimeMillis();
     
     int count = 0;
     int index = s.indexOf(toSearch);
     while (index != -1)
     {
       index++;
       count++;
       index = s.indexOf(toSearch, index);
     }
     
     
     System.out.println("Number of " + toSearch + ": " + count);
System.out.println("Time: " + (end - start) + " ms");
 }
 
 //returns a String of length l with lowercase letters from a to z
  static String randomString(int len)
  {
   char[] cr = new char[len];
   Random rd = new Random();
   for (int i = 0; i < len; i++){
   int num = rd.nextInt(26) + 97;
   cr [i] = (char) num;
   }
  
     return new String(cr);
    
  }

}