SymPy | Python中的 Permutation.unrank_lex()

Permutation.unrank_lex() ：unrank_lex()是一个 sympy Python库函数，它返回字典排列 unranking。

Syntax : sympy.combinatorics.permutations.Permutation.unrank_lex()

Return : Lexicographic permutation unranking

代码 #1：unrank_lex() 示例

# Python code explaining
# SymPy.Permutation.unrank_lex()
  
# importing SymPy libraries
from sympy.combinatorics.partitions import Partition
from sympy.combinatorics.permutations import Permutation
  
# Using from sympy.combinatorics.permutations.Permutation.unrank_lex() method 
  
# creating Permutation
a = Permutation([[2, 0], [3, 1]])
  
b = Permutation([1, 3, 5, 4, 2, 0])
  
size = 2
rank = 5
  
print ("Permutation a - unrank_lex form : ", a.unrank_lex(size, rank))
print ("Permutation b - unrank_lex form : ", b.unrank_lex(size, 2))

输出 ：

Permutation a – unrank_lex form : (0 1)
Permutation b – unrank_lex form : (1)

代码 #2：unrank_lex() 示例

# Python code explaining
# SymPy.Permutation.unrank_lex()
  
# importing SymPy libraries
from sympy.combinatorics.partitions import Partition
from sympy.combinatorics.permutations import Permutation
  
# Using from 
# sympy.combinatorics.permutations.Permutation.unrank_lex() method 
  
# creating Permutation
a = Permutation([[2, 4, 0], 
                 [3, 1, 2],
                 [1, 5, 6]])
  
  
print ("Permutation a - unrank_lex form : ", a.unrank_lex(5, 2))

输出 ：

Permutation a – unrank_lex form : (4)(2 3)