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  1. #include <stdio.h>
  2. #include <stdlib.h>
  3. #include <limits.h>
  4.  
  5. int multimerge(
  6.     int * const * const arrays,      // arrays holding the data
  7.     int const * const arraysizes,    // sizes of the arrays in `arrays`
  8.     int number_of_arrays,            // number of arrays
  9.     int * const output               // pointer to output buffer
  10. ){
  11.     int i = 0;       // output cursor
  12.     int j = 0;       // index for minimum search
  13.     int min;         // minimum in this iteration
  14.     int minposition; // position of the minimum
  15.  
  16.     // cursor for the arrays
  17.     int * cursor = calloc(number_of_arrays,sizeof(int));
  18.  
  19.     if(cursor == NULL)
  20.         return -1;
  21.  
  22.     while(1){
  23.         min = INT_MAX;
  24.         minposition = -1; // invalid position
  25.  
  26.         // Go through the current positions and get the minimum
  27.         for(j = 0; j < number_of_arrays; ++j){
  28.  
  29.             if(cursor[j] < arraysizes[j] &&  // ensure that the cursor is still valid
  30.                arrays[j][cursor[j]] < min){  // the element is smaller
  31.                 min = arrays[j][cursor[j]];  // save the minimum ...
  32.                 minposition = j;             // ... and its position
  33.             }
  34.         }
  35.  
  36.         // if there is no minimum, then the position will be invalid
  37.  
  38.         if(minposition == -1)
  39.             break;
  40.  
  41.         // update the output and the specific cursor            
  42.         output[i++] = min;
  43.         cursor[minposition]++;
  44.     }
  45.     free(cursor);
  46.  
  47.     return 0;
  48. }
  49.  
  50. int main()
  51. {
  52.     int i = 0;
  53.     int test1[5] = {23, 24, 25, 33, 51};
  54.     int test2[5] = {21, 34, 44, 50, 62};
  55.     int test3[5] = {34, 36, 41, 44, 46};
  56.     int test4[5] = {30, 31, 32, 35, 40};
  57.     int test5[5] = {54, 56, 57, 58, 60};
  58.     int test6[5] = {31, 33, 36, 51, 52};
  59.     int test7[5] = {44, 46, 76, 78, 79};
  60.     int test8[5] = {23, 33, 43, 54, 63};
  61.  
  62.     int *test[] = {test1, test2, test3, test4, test5, test6, test7, test8};
  63.     int testsizes[] = {5,5,5,5,5,5,5,5};
  64.  
  65.     int output[40];
  66.  
  67.     multimerge(test,testsizes,8,output);
  68.  
  69.     while(i < 30){
  70.         printf("%i\n",output[i++]);
  71.     }    
  72.  
  73.     return 0;
  74. }
  75.  
Success #stdin #stdout 0.02s 1808KB
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https://ideone.com/VZzZL
language:
C (gcc 8.3)
created:
13 years ago
visibility:
public

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