Tasks and Solutions: Pointers C ++

40 thoughts on “Tasks and Solutions: Pointers C ++”

1. Overall good. Didn't read into it, looked diagonally. The pictures are beautiful.

   I would not write functions like giveMemoryToArr (although, for taste and color…).
   If we leave them, then IMHO double* freeMemory(double* ptrArr) should return void. Why does it always return zero??

   Some other example (more voluminous)… Checkers (man against man) whether…

   Generally, well done. Write more :)

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2. Thank you very much to the admin, за то, which gives not only tasks, and solutions with detailed comments to the code. I read C++ tutorials on several sites. On your – I like it the most. Convenient home page content, problems with solutions on a separate page. Why are tasks grouped by topic?, and not everything in a crowd and mixed up.
   Don't stop! Write more! :)

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3. So maybe the task can be done 3 and solve without buffers:
   void mixmass(int no, int *arr)
   {
   for (int i = 1; i < sz; i )
   {
   if (arr[i] % 2 == 0)
   arr[i] = i-1;
   }
   }
   ————————————————————–
   for (int i = 0; i < sz; i )
   {
   mass [i] = i+1;
   std::cout << mass [i] << std::ends;
   };

   mixmass(sz, mass);

   But I don't get it..

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4. The first problem contains a bunch of incomprehensible structures, there were no explanations for them in previous lessons, so why solve the problem in a way, which is not clear to students?

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   1. In the 1st problem there are no “designs” – you just need to understand it well, what:
      a). the pointer contains адрес Togo, what is he pointing to,
      b). and the operation denaming a pointer (prefix operation *) means: “take value Togo, what does the pointer point to?”.

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      1. This I know, it was in the lesson. But 4 string, where void is in parentheses, I can't understand at all, there was never anything in parentheses in the lessons;
         String 6, where nothing is clear at all, there were no such structures in the lessons. The tasks should be like this, that after reading all the previous articles they could be easily understood. But the first task is not like that at all.

5. 3 a task

   #include
   using namespace std;

   int main()
   {
   setlocale(LC_ALL, “rus”);
   system(“color E0”);

   int* array = new int[12];
   for (int i = 0; i < 12; i )
   {
   array[i] = i + 1;
   cout << array[i] << " ";
   }

   cout << endl;

   int b = 0;
   int j = 1;
   int save = 0;
   for (int i = 0; i < 6; i )
   {
   save = array[b];
   array[b] = array[j];
   array[j] = save;

   b = b + 2;
   j = j + 2;
   }

   for (int i = 0; i < 12; i )
   {
   cout << array[i] << " ";
   }

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6. Guys, if it's not difficult, help me with the problem: Given are matrices A and B of size k×m and m×l, respectively. Find the product AB. Implement matrix multiplication as a function.

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   1. The matrix multiplication problem itself – “if it's not difficult” (and even elementary – 2 nested loop).
      But:
      1. There are different options for representing 2-dimensional matrices (as 2-dimensional arrays, like arrays of pointers, like STL containers – vector of vectors, etc.. … to 10 different ways or more). Depending on the chosen method, calculations will be written completely differently..
      2. Much larger in volume, than multiplication itself, will take you a). input of initial matrices + b). output result + in). test task main() which will clearly demonstrate the process and result.

      So the task is very simple, but write everything for it framing – not at all easy, there is a lot of mechanical work.

      Reply

7. People, what if I want to write a function for allocating memory for a two-dimensional array, what does it look like.

   int *givemmry (int **boob, int size1,int size2)
   {
   **boob = new int* [size1];
   for (int i = 0; i < size1; i )
   {
   boob[i] = new int[size2];
   }
   return **boob;
   }

   so it gives an error

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   1. 
int** givemmry( int size1, int size2 ) {
int **boob = new int* [ size1 ];
for( int i = 0; i < size1; i++ )
boob[ i ] = new int[ size2 ];
return boob;
}

      Or easier:
      
int** givemmry( int size1, int size2 ) {
return (int**)new int* [ size1 * size2 ];
}


      Reply

      1. In the 2nd solution, an error crept in by copying, there must be, naturally:
         
int** givemmry( int size1, int size2 ) {
return (int**)new int [ size1 * size2 ];
}


8. Thank you! as I understand it, it is not necessary to specify the type and index of the array (boob) in function argument, we just return the value?

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   1. Here the parameter turns out to be simply superfluous – you will still overwrite its value after new, and his type (and array elements) you still can't change it.

      Reply