Python| SymPy Permutation.index() 方法

Permutation.index() : index()是一个 sympy Python库函数，它返回参数中排列的索引值。

排列的索引 =所有下标 j 的总和，使得 permutation[j] 大于 permutation[j+1]。

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

Return :
index value of the permutation

代码 #1：index() 示例

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

输出 ：

Permutation a – index form : 1
Permutation b – index form : 9

代码 #2 : index() 示例– 2D 排列

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

输出 ：

Permutation a – index form : 8