Given a List, write a Python program to find the span of even elements in list, i.e distance between first and last occurrence of even element.
Examples:
Input : test_list = [1, 3, 7, 4, 7, 2, 9, 1, 10, 11]
Output : 5
Explanation : Even elements begin at 4 and end at 10, spanning 5 indices.
Input : test_list = [1, 3, 7, 4, 7, 2, 9, 1, 1, 11]
Output : 2
Explanation : Even elements begin at 4 and end at 2, spanning 2 indices.
Method #1: Using list comprehension
In this we get all the indices of all even elements using list comprehension and then perform difference of first and last index of matched elements in list.
Python3
# Python3 code to demonstrate working of# Even elements span in list# Using list comprehension # initializing Matrixtest_list = [1, 3, 7, 4, 7, 2, 9, 1, 10, 11] # printing original listprint("The original list is : " + str(test_list)) # getting even indicesindices_list = [idx for idx in range( len(test_list)) if test_list[idx] % 2 == 0] # getting difference of first and last occurrenceres = indices_list[-1] - indices_list[0] # printing resultprint("Even elements span : " + str(res)) |
The original list is : [1, 3, 7, 4, 7, 2, 9, 1, 10, 11] Even elements span : 5
Method #2 : Using filter() + lambda
In this, we perform task of getting indices of elements using filter() and lambda.
Python3
# Python3 code to demonstrate working of# Even elements span in list# Using filter() + lambda # initializing Matrixtest_list = [1, 3, 7, 4, 7, 2, 9, 1, 10, 11] # printing original listprint("The original list is : " + str(test_list)) # getting even indicesindices_list = list( filter(lambda x: test_list[x] % 2 == 0, range(len(test_list)))) # getting difference of first and last occurrenceres = indices_list[-1] - indices_list[0] # printing resultprint("Even elements span : " + str(res)) |
The original list is : [1, 3, 7, 4, 7, 2, 9, 1, 10, 11] Even elements span : 5
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