Thread: C++ compare two arrays and display duplicates

Here, look at this:

Code:

for(int i = 0; i < sizeof(alphabetArray);i++ )    
   {

      countFreq = 0;
              
      for(int j = 0; j < sizeof(buffer); j++)
         {    
           if( alphabetArray[i] == buffer[j] )
              countFreq = countFreq + 1;
         }

       if(countFreq > 0)
           cout << "The letter " << alphabetArray[i] << "  matched " .......
       

    }

By having cout after the inner for loop but before looping back to the start of the outer loop you can leave i++ where it was. Also, use if(countFreq > 0) to skip printing on those letters where there wasn't a match (if you want).

Also, it looks like maybe you are printing out one too many lines? Maybe j < sizeof(buffer) should be j < sizeof(buffer)-1 ? And manybe the same for sizeof(alphabetArray)? You decide what, if anything, needs to be done.

Although it is correct, instead of writing this:

Code:

char alphabetArray[]={'a','b','c','d','e','f','g','h','i','j','k',
    'l','m','n','o','p','q','r','s','t','u','v','w','x','y','z','\0'};

Write the more concise version:

Code:

char alphabetArray[] = "abcdefghijklmnopqrstuvwxyz";

Next, note that when used on an array, the sizeof operator results in the number of bytes of the elements of the array. alphabetArray actually contains 27 elements, each of one byte. As such, your loop that loops through alphabetArray also accesses alphabetArray[26], which is a null character. It probably does not make sense to include that, so it would be better to use strlen instead of sizeof (e.g., call strlen(alphabetArray) once just before the loop, then use the return value), or to subtract one.

As a matter of style, we would typically write this:

Code:

countFreq = countFreq + 1;

as:

Code:

++countFreq;

Finally, it is good to see that you have used indentation to show the structure of your code, but you could be a little more consistent, e.g.,

Code:

   // loop through alphabet array
    for(int i = 0; i < sizeof(alphabetArray); )
    {
     cout << "The letter " << alphabetArray[i] << "  matched " << countFreq << " times." << endl;
     i++;
     countFreq = 0;
            
      for(int j = 0; j < sizeof(buffer); j++)
       {   
        if( alphabetArray[i] == buffer[j] )
           countFreq = countFreq + 1;
       }
    }

could have been:

Code:

    // loop through alphabet array
    for(int i = 0; i < sizeof(alphabetArray); )
    {
        cout << "The letter " << alphabetArray[i] << "  matched " << countFreq << " times." << endl;
        i++;
        countFreq = 0;
    
        for(int j = 0; j < sizeof(buffer); j++)
        {   
            if( alphabetArray[i] == buffer[j] )
                countFreq = countFreq + 1;
        }
    }

Hello Coder Head and Laserlight,
All of your suggestions have been great to learn from.
For the record, this practice project does include outputting
all of the letters of the alphabet, matches and no matches.
I am attaching the finished code. I am going to submit another version using the ASCII table and some new member functions.
In the meantime, here it is with a nice definition of strlen commented in:

Code:

#include <iostream>
#include <iomanip>
#include <string>
#include <algorithm>
#include <Windows.h>

using namespace std;

bool checkBuffer( char buffArray[], int buffSize );
void parseBuffer( char alphaArray[], char buffArray[], int alphaSize, int buffSize );

int main() 
{
    char alphabetArray[]= "abcdefghijklmnopqrstuvwxyz";
    char buffer[11];
        
    cout << "Enter the string up to 10 letters." << endl;
    cin.get(buffer, strlen(buffer) );
    
    checkBuffer(buffer, strlen(buffer) );
    parseBuffer( alphabetArray, buffer, strlen(alphabetArray), strlen(buffer) );
    
     // www.cplusplus.com definition of strlen:
     //char mystr[100]="test string"; defines an array of characters with a size of 100 chars,_
     // but the C string with which "mystr" has been initialized has a length of only 11 characters._
     // Therefore, while "sizeof(mystr)" evaluates to 100, "strlen(mystr)" returns 11.
    
    system("Pause");
    return 0;
}
bool checkBuffer( char buffArray[], int buffSize )
{
    if(buffArray, strlen(buffArray) == 0)
     {
        cout << "The buffer is empty.  The program will end in 3 seconds. "  << endl;
        Sleep(3000);
     }
        exit(1);
}     
void parseBuffer( char alphaArray[], char buffArray[], int sizeOne, int sizeTwo )
{
      int countFreq = 0;
      for(int i = 0; i < strlen(alphaArray); i++ )
       {
         countFreq = 0; 
           
       for(int j = 0; j < strlen(buffArray); j++)
        {    
             if( alphaArray[i] == buffArray[j] )
             countFreq = countFreq + 1;
        }
             cout << "The letter " << alphaArray[i] << "  matched " << countFreq << " times." << endl; 
      }
}

-----------------------
OUTPUT:
Enter the string up to 10 letters.
itsahwzome
The letter a matched 1 times.
The letter b matched 0 times.
The letter c matched 0 times.
The letter d matched 0 times.
The letter e matched 1 times.
The letter f matched 0 times.
The letter g matched 0 times.
The letter h matched 1 times.
The letter i matched 1 times.
The letter j matched 0 times.
The letter k matched 0 times.
The letter l matched 0 times.
The letter m matched 1 times.
The letter n matched 0 times.
The letter o matched 1 times.
The letter p matched 0 times.
The letter q matched 0 times.
The letter r matched 0 times.
The letter s matched 1 times.
The letter t matched 1 times.
The letter u matched 0 times.
The letter v matched 0 times.
The letter w matched 1 times.
The letter x matched 0 times.
The letter y matched 0 times.
The letter z matched 1 times.
Press any key to continue . . .

Err... now you're overdoing the strlen

The idea behind strlen is that you have strings and you want to loop over the characters in the strings.

The thing is, when you're reading into buffer, buffer is just an array that does not contain a string, therefore sizeof(buffer) is correct whereas strlen(buffer) is wrong.