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  1. #include <iostream>
  2. #include <numeric>
  3. #include <vector>
  4.  
  5. int pCount(int n, int m, int myMax) {
  6.  
  7.     if (myMax * m < n) return 0;
  8.     if (myMax * m == n) return 1;
  9.  
  10.     if (m < 2) return m;
  11.     if (n < m) return 0;
  12.     if (n <= m + 1) return 1;
  13.  
  14.     int niter = n / m;
  15.     int count = 0;
  16.  
  17.     for (; niter--; n -= m, --myMax) {
  18.         count += pCount(n - 1, m - 1, myMax);
  19.     }
  20.  
  21.     return count;
  22. }
  23.  
  24. std::vector<int> unRank(int n, int m, int myMax, int nth) {
  25.  
  26.     std::vector<int> z(m, 0);
  27.     int count = 0;
  28.     int j = 0;
  29.  
  30.     for (int i = 0; i < z.size(); ++i) {
  31.         int temp = pCount(n - 1, m - 1, myMax);
  32.  
  33.         for (int r = n - m, k = myMax - 1;
  34.              (count + temp) < nth && r > 0 && k; r -= m, --k) {
  35.  
  36.             count += temp;
  37.             n = r;
  38.             myMax = k;
  39.             ++j;
  40.             temp = pCount(n - 1, m - 1, myMax);
  41.         }
  42.  
  43.         --m;
  44.         --n;
  45.         z[i] = j;
  46.     }
  47.  
  48.     return z;
  49. }
  50.  
  51. int main() {
  52. 	int max = 10;
  53. 	int min = 3;
  54. 	int N = 7;
  55. 	int sum = 42;
  56.  
  57.     int m = N;
  58.     int n = sum - m * (min - 1);
  59.     int myMax = max - min + 1;
  60.     int totalNum = pCount(n, m, myMax);
  61.     int index = 100;
  62.  
  63.     std::vector<int> z = unRank(n, m, myMax, index);
  64.  
  65.     std::vector<int> v(max - min + 1);
  66.     std::iota(v.begin(), v.end(), min);
  67.  
  68.     for (int i = 0; i < m; ++i)
  69.         std::cout << v[z[i]] << ", ";
  70.  
  71.     std::cout << std::endl;
  72.     return 0;
  73. }
Success #stdin #stdout 0s 4540KB
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4, 4, 4, 5, 6, 9, 10,
https://ideone.com/oFk6vj
language:
C++ (gcc 8.3)
created:
5 years ago
visibility:
public

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