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  1.     #include <algorithm>
  2.     #include <iostream>
  3.  
  4.     struct IndexSorter
  5.     {
  6.        double *m_array;
  7.        IndexSorter(double *oArray) : m_array(oArray) {}
  8.        bool operator()(long v1, long v2) const { return m_array[v1] < m_array[v2]; }
  9.     };
  10.  
  11.     long* IndexSort(unsigned long int vectorLength, double* column)
  12.     {
  13.         long *index = new long[vectorLength](); // I really don't recommend this line
  14.         for (unsigned long i = 0; i < vectorLength; ++i) 
  15.             index[i] = i;
  16.  
  17.         std::sort(index, index + vectorLength, IndexSorter(column));
  18.         return index;
  19.     }
  20.  
  21.     using namespace std;
  22.  
  23.     int main()
  24.     {  
  25.       double testData[] =   {0.8147,0.9058,0.127,0.9134,0.6324,0.0975,0.2785,
  26.                             0.5469,0.9575,0.9649,0.1576,0.9706,0.9572,0.4854,
  27.                             0.8003,0.1419,0.4218,0.9157,0.7922,0.9595};
  28.       unsigned long testSize = sizeof(testData) / sizeof(testData[0]);
  29.       long *indices = IndexSort(testSize, &testData[0]);
  30.       for (unsigned long i = 0; i < testSize; ++i )
  31.         cout << testData[indices[i]] << "  has an index of " << indices[i] << "\n";
  32.       delete [] indices;
  33.     }
  34.  
  35.  
Success #stdin #stdout 0s 2816KB
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stdin
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Standard input is empty
stdout
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0.0975  has an index of 5
0.127  has an index of 2
0.1419  has an index of 15
0.1576  has an index of 10
0.2785  has an index of 6
0.4218  has an index of 16
0.4854  has an index of 13
0.5469  has an index of 7
0.6324  has an index of 4
0.7922  has an index of 18
0.8003  has an index of 14
0.8147  has an index of 0
0.9058  has an index of 1
0.9134  has an index of 3
0.9157  has an index of 17
0.9572  has an index of 12
0.9575  has an index of 8
0.9595  has an index of 19
0.9649  has an index of 9
0.9706  has an index of 11
https://ideone.com/nhMwSs
language:
C++ 4.3.2 (gcc-4.3.2)
created:
10 years ago
visibility:
public

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