Given a list of lists, where each sublist consists of only two elements, write a Python program to merge the first and last element of each sublist separately and finally, output a list of two sub-lists, one containing all first elements and other containing all last elements.
Examples:
Input : [['x', 'y'], ['a', 'b'], ['m', 'n']] Output : [['x', 'a', 'm'], ['y', 'b', 'n']] Input : [[1, 2], [3, 4], [5, 6], [7, 8]] Output : [[1, 3, 5, 7], [2, 4, 6, 8]]
Approach #1 : List comprehension and zip
Python3
# Python3 program to Merge first and last# elements separately in a list of listsdef merge(lst): return [list(ele) for ele in list(zip(*lst))]# Driver codelst = [['x', 'y'], ['a', 'b'], ['m', 'n']]print(merge(lst)) |
[['x', 'a', 'm'], ['y', 'b', 'n']]
Time Complexity: O(n), where n is the length of the list test_list
Auxiliary Space: O(n) additional space of size n is created where n is the number of elements in the list
Approach #2 : Using Numpy array First convert the given list to numpy array and then return transpose of the array, and finally convert the array to list.
Python3
# Python3 program to Merge first and last# elements separately in a list of listsimport numpy as npdef merge(lst): arr = np.array(lst) return arr.T.tolist() # Driver codelst = [['x', 'y'], ['a', 'b'], ['m', 'n']]print(merge(lst)) |
[['x', 'a', 'm'], ['y', 'b', 'n']]
Time Complexity: O(n), where n is the length of the list test_list
Auxiliary Space: O(n) additional space of size n is created where n is the number of elements in the list
Approach #3 : Using for loop + extend() method
Python3
# Python3 program to Merge first and last# elements separately in a list of listslst = [['x', 'y'], ['a', 'b'], ['m', 'n']]a = []for i in lst: a.extend(i)x = []y = []for i in range(0, len(a)): if(i % 2 == 0): x.append(a[i]) else: y.append(a[i])res = []res.append(x)res.append(y)print(res) |
[['x', 'a', 'm'], ['y', 'b', 'n']]
