Python| SymPy Permutation.descents() 方法

Permutation.descents() ：descents()是一个 sympy Python库函数，它返回置换中下降的位置。下降是a[i] > a[i+1]的元素

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

Return : position of descents in the permutation

代码 #1：descents() 示例

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

输出 ：

Permutation a – descents form : [1]
Permutation b – descents form : [2, 3, 4]

代码 #2：descents() 示例– 2D 排列

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

输出 ：

Permutation a – descents form : [0, 3, 5]