用偶数频率元素提取矩阵行的Python程序

给定一个矩阵，任务是编写一个Python程序来提取所有元素频率为偶数的行。

例子：

Input: [[4, 5, 5, 2], [4, 4, 4, 4, 2, 2], [6, 5, 6, 5], [1, 2, 3, 4]]

Output: [[4, 4, 4, 4, 2, 2], [6, 5, 6, 5]]

Explanation: 

• frequency of 4-> 4 which is even
• frequency of 2-> 2 which is even
• frequency of 6-> 2 which is even
• frequency of 5-> 2 which is even

方法 1：使用列表理解、 Counter()和all()

其中，count 使用 Counter() 进行维护，all() 用于检查所有频率是否为偶数，如果不是，则不会在结果列表中输入行。

程序：

Python3

from collections import Counter
  
# initializing list
test_list = [[4, 5, 5, 2], [4, 4, 4, 4, 2, 2],
             [6, 5, 6, 5], [1, 2, 3, 4]]
  
# printing original list
print("The original list is : " + str(test_list))
  
# Counter() gets the required frequency
res = [sub for sub in test_list if all(
    val % 2 == 0 for key, val in list(dict(Counter(sub)).items()))]
  
# printing result
print("Filtered Matrix ? : " + str(res))

输出：

The original list is : [[4, 5, 5, 2], [4, 4, 4, 4, 2, 2], [6, 5, 6, 5], [1, 2, 3, 4]]

Filtered Matrix ? : [[4, 4, 4, 4, 2, 2], [6, 5, 6, 5]]

方法 2：使用filter() 、 Counter()和 items()

与上述方法类似，不同之处在于 filter() 和 lambda函数用于过滤偶数行的任务。

程序：

蟒蛇3

from collections import Counter
  
# initializing list
test_list = [[4, 5, 5, 2], [4, 4, 4, 4, 2, 2], 
             [6, 5, 6, 5], [1, 2, 3, 4]]
  
# printing original list
print("The original list is : " + str(test_list))
  
# Counter() gets the required frequency
# filter() used to perform filtering
res = list(filter(lambda sub: all(val % 2 == 0 for key,
                                  val in list(dict(Counter(sub)).items())), test_list))
  
# printing result
print("Filtered Matrix ? : " + str(res))

输出：

The original list is : [[4, 5, 5, 2], [4, 4, 4, 4, 2, 2], [6, 5, 6, 5], [1, 2, 3, 4]]

Filtered Matrix ? : [[4, 4, 4, 4, 2, 2], [6, 5, 6, 5]]