I'm new at C and I'm trying to solve this problem. Here is the code.

#include <iostream>
#include <ctime>
#include <cstdlib>

using namespace std;

int my_rand_arr(int a, int b);
void random_arr(int arr[], int n);
void output_arr(int arr[], int n);

int main(){
  srand(time(0));
  const int N = 20;
  int arr[N];

  random_arr(arr, N);
  output_arr(arr, N);

return 0;
}

int my_rand_arr(int a, int b){
  return rand() % (b - a   1)   a;
}

void random_arr(int arr[], int n){
    for(int i = 0; i < n; i  ){
    arr[i] = my_rand_arr(1, 6);
  }
}

void output_arr(int arr[], int n){
    for(int i = 0; i < n; i  ){
      if(arr[i] == arr[i   1]){
        cout << "(";
      }   
    cout << arr[i] << " ";
  }  
  cout << endl;
}

It is random array and the thing I'm trying to achieve is that if there is a couple of equal adjacent numbers, those numbers will be written inside brackets.

Expected output:
1 6 3 (1 1) 6 2 (4 4 4) 3 6 1 5 6 5 2 1 (5 5)

What should I do in order to achieve that output?

CodePudding user response：

Just count the number of repetitons of each element and print the elements when reaching the a different element or the end of the array.

void output_arr(int arr[], size_t const n) {
    auto pos = arr;
    auto const end = arr   n;

    while (pos != end)
    {
        size_t count = 1;
        auto const element = *pos;

        for (  pos; pos != end && *pos == element;   pos,   count)
        {
        }

        if (count == 1)
        {
            std::cout << element << ' ';
        }
        else
        {
            std::cout << '(' << element;
            for (; count != 1; --count)
            {
                std::cout << ' ' << element;
            }
            std::cout << ") ";
        }
    }
    std::cout << '\n';
}

int main() {

    int arr[] = { 1, 6, 3, 1, 1, 6, 2, 4, 4, 4, 3, 6, 1, 5, 6, 5, 2, 1, 5, 5 };
    output_arr(arr, sizeof(arr) / sizeof(*arr));
}

CodePudding user response：

Before evaluating the expression arr[i] == arr[i 1], you must verify that n 1 is not out of bounds of the array. Otherwise your program will invoke undefined behavior.

Here is my solution to the problem:

#include <iostream>

void output_arr( int arr[], int n )
{
    for ( int i = 0; i < n; i   )
    {
        //determine whether there are adjacent identical numbers
        if ( i   1 != n && arr[i] == arr[i 1] )
        {
            //only add space if we are not at the start of the line
            if ( i != 0 )
                std::cout << ' ';

            //print opening parenthesis and first number of repetition
            std::cout << '(' << arr[i];

            //print remaining numbers of repetition
            do
            {
                i  ;
                std::cout << ' ' << arr[i];

            } while ( i   1 != n && arr[i] == arr[i 1] );

            //print closing parenthesis
            std::cout << ')';
        }
        else
        {
            //only add space if we are not at the start of the line
            if ( i != 0 )
                std::cout << ' ';

            //print non-repeating number without parentheses
            std::cout << arr[i];
        }
    }

    //finish line
    std::cout << '\n';
}

int main()
{
    int arr[] = { 1, 6, 3, 1, 1, 6, 2, 4, 4, 4, 3, 6, 1, 5, 6, 5, 2, 1, 5, 5 };

    output_arr( arr, sizeof arr / sizeof *arr );
}

This program has the desired output:

1 6 3 (1 1) 6 2 (4 4 4) 3 6 1 5 6 5 2 1 (5 5)