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  1. m = {1: 2, 7: 3, 2: 1, 4: 4, 5: 3, 6: 9}
  2. n = {1:2, 2:3, 3:4, 4:5, 5:1, 6:1, 7:1, 8:8}
  3.  
  4. cycles = set()
  5. for k, v in m.items():
  6.     if m.get(v) == k:
  7.         cycles.add(tuple(sorted((k, v))))
  8.  
  9. output = [[k] if k == v else (k, v) for k, v in cycles]
  10. print(output)
  11.  
  12. cycles = set(tuple(sorted(item)) for item in m.items() if m.get(item[1]) == item[0])
  13.  
  14.  
  15. output = [[k] if k == v else (k, v) for k, v in cycles]
  16. print(output)
  17.  
  18. def find_cycles(m):
  19.     n = m.copy()  # don't mutilate the original
  20.     cycles = []
  21.     while n:
  22.         visited = {}
  23.         count = 0
  24.         k, v = n.popitem()
  25.         while v is not None:
  26.             visited[k] = (count, v)
  27.             count += 1
  28.             k = v
  29.             v = n.pop(k, None)
  30.  
  31.         if k in visited:
  32.             cycle_start = visited[k][0]
  33.             item = min((k, v) for k, (c, v) in visited.items() if c >= cycle_start)
  34.             cycles.append(item)
  35.  
  36.     return [[k] if k == v else (k, v) for k, v in cycles]
  37.  
  38. print(find_cycles(m))
  39. print(find_cycles(n))
  40.  
  41. def find_cycles(m):
  42.     n = m.copy()  # don't mutilate the original
  43.     cycles = []
  44.     while n:
  45.         visited = {}
  46.         count = 0
  47.         k, v = n.popitem()
  48.         while v is not None:
  49.             visited[k] = count
  50.             count += 1
  51.             k = v
  52.             v = n.pop(k, None)
  53.  
  54.         if k in visited:
  55.             if len(visited) == 1:
  56.                 cycle = list(visited.keys())
  57.             else:
  58.                 cycle_start = visited[k]
  59.                 cycle = sorted((c, k) for k, c in visited.items() if c >= cycle_start)
  60.                 cycle = tuple(k for c, k in cycle)
  61.                 k = min(range(len(cycle)), key=lambda x: cycle[x])
  62.                 cycle = cycle[k:] + cycle[:k]
  63.             cycles.append(cycle)
  64.  
  65.     return cycles
  66.  
  67. print(find_cycles(m))
  68. print(find_cycles(n))
Success #stdin #stdout 0.02s 27712KB
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Standard input is empty
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[(1, 2), [4]]
[(1, 2), [4]]
[(1, 2), [4]]
[(1, 2), [8]]
[(1, 2), [4]]
[(1, 2, 3, 4, 5), [8]]
https://ideone.com/6kpRrW
language:
Python 3 (python  3.12)
created:
6 years ago
visibility:
public

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