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  1. #include <stdlib.h>
  2. #include <stdio.h>
  3.  
  4. static double *myArray;
  5.  
  6. int compareIndices(const void* v1, const void *v2)
  7. {
  8.     long val1 = *(long *)v1;
  9.     long val2 = *(long *)v2;
  10.     if (myArray[val1] < myArray[val2])
  11.         return -1;
  12.     else
  13.     if ( myArray[val1] > myArray[val2])
  14.         return 1;
  15.     return 0;
  16. }
  17.  
  18. long* IndexSort(unsigned long int vectorLength, double* column)
  19. {
  20.     myArray = column;
  21.     long *index = malloc(vectorLength * sizeof(long));
  22.     if ( index )
  23.     {
  24.         unsigned long i;
  25.         for (i = 0; i < vectorLength; ++i)
  26.             index[i] = i;
  27.         qsort(index, vectorLength, sizeof(long), compareIndices);
  28.         return index;
  29.     }
  30.     return 0;
  31. }
  32.  
  33. int main()
  34. {
  35.     double testData[] = { 0.8147, 0.9058, 0.127, 0.9134, 0.6324, 0.0975, 0.2785,
  36.         0.5469, 0.9575, 0.9649, 0.1576, 0.9706, 0.9572, 0.4854,
  37.         0.8003, 0.1419, 0.4218, 0.9157, 0.7922, 0.9595 };
  38.     unsigned long numItems = sizeof(testData) / sizeof(testData[0]);
  39.     long *indices = IndexSort(numItems, testData);
  40.     if ( indices )
  41.     {
  42.         for (unsigned long i = 0; i < numItems; ++i)
  43.             printf("%lf has an index of %ld\n", testData[indices[i]], indices[i]);
  44.         free(indices);
  45.     }
  46. }
Success #stdin #stdout 0s 2140KB
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stdin
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Standard input is empty
stdout
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0.097500 has an index of 5
0.127000 has an index of 2
0.141900 has an index of 15
0.157600 has an index of 10
0.278500 has an index of 6
0.421800 has an index of 16
0.485400 has an index of 13
0.546900 has an index of 7
0.632400 has an index of 4
0.792200 has an index of 18
0.800300 has an index of 14
0.814700 has an index of 0
0.905800 has an index of 1
0.913400 has an index of 3
0.915700 has an index of 17
0.957200 has an index of 12
0.957500 has an index of 8
0.959500 has an index of 19
0.964900 has an index of 9
0.970600 has an index of 11
https://ideone.com/8SZH1m
language:
C99 (gcc 8.3)
created:
10 years ago
visibility:
public

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