For example i have an array {1,2,2,2,3,3,3,3,4,4,4,4,4,} I need to transform it into {4,4,4,4,4,,3,3,3,3,2,2,2,1} So i have to sort it by the number of repetitions of an array element somehow. I saw some solves of this problem on c but i have to write it on C. I can`t use vector or smth. Just Sorting with buffer array or inside of exact array.

I tried something like this, but honestly now i etched into a dead end: It is dont work properly as i ment. I have an algoritm in my head:

1. Program count how times some element was repeated and write in into a second array
2. Program sort second array
3. Program sort first array by second array somehow

#include <stdio.h>

int main()
{
    const int size = 10;
    int A[size], B[size];
    int counter1, counter2 = -1;
    int temp = 0;
    
    for (int i = 0; i < size; i  ) {
        printf("Enter %d element of array: ", i   1);
        scanf_s("%d", &A[i]);
    }
    for (int i = 0; i < size-1; i  ) {
        counter1 = 0;
        counter2  ;
        for (int j = i; j < size; j  ) {
            if (A[j] == A[j - 1]) {
                break;
            }
            if (A[j] == A[j 1]) {
                counter1  ;
                B[counter2] = counter1;
                temp = A[i];
            }
        }
    }
    for (int i = 0; i < size; i  ) {
        printf("El %d = %d\n",i 1,B[i]);
    }
}

CodePudding user response：

Not the best, but it does the job! I'm storing the final result in the Result[len][2]; variable! you can modify the code as you like

#include <stdio.h>
#include <string.h>

int main( )
{  
    int array[] = {1,2,2,2,3,3,3,3,4,4,4,4,4,11,10,6,6,6,6,6,6,6,6,6,6,6,6,};
    int i,j,k=0,l,len,flag=0,temp0, temp1;
    len = sizeof(array)/sizeof(array[0]);
    int Result[len][2];
    memset(Result,0,sizeof(Result));

    for (i = 0 ;i < len ; i   )
    {       
        if (k != 0)
        {
            for (l= 0 ;l < k ; l   )
            if (array[i]== Result[l][0]) goto skip;    
        }
        for(j= i ; j < len ; j   )                
        {  
            if (array[i] == array[j])
            {                
                Result[k][0] = array[j];  
                Result[k][1]  ;flag = 1;
            }
        }   
        skip: if (flag == 1) {k  ; flag = 0;}
    }

     for (i = 0; i < k; i  )
     {
         for(j= i 1 ; j < k ; j   )        
         {
             if(Result[i][1] < Result[j][1])
               {   
                   temp0  = Result[i][0];
                   temp1  = Result[i][1]; 
                   Result[i][0] = Result[j][0];
                   Result[i][1] = Result[j][1];                   
                   Result[j][0]  = temp0 ;
                   Result[j][1]  = temp1 ;                   
               }
         }
     }

    for (i = 0; i < k; i  ) printf("[%d][%d]\n",Result[i][0],Result[i][1]);     

    return 0;
}

The output at my computer under the Linux environment is as follows:

[6][12]
[4][5]
[3][4]
[2][3]
[11][1]
[10][1]
[1][1] 

CodePudding user response：

how can I sort an array by the number of repetitions

1. Sort array A of size m by value .

2. Walk array and count number of different values: n

3. Allocate array B[] of size n of structs that has 2 members: value and occurrence.

4. Walk array A[] again and populate B[]

5. Sort B[] by .occurrence.

6. Walk B[] and re-populate A[].

O(m) memory, O(m *log m) time.