Given a two-dimensional list of integers, write a Python program to get the transpose of given list of lists.
In Python, a matrix can be interpreted as a list of lists. Each element is treated as a row of the matrix. For example m = [[10, 20], [40, 50], [30, 60]] represents a matrix of 3 rows and 2 columns. First element of the list – m[0] and element in first row, first column – m[0][0].
Example:
Input : l1 = [[4, 5, 3, 9],
[7, 1, 8, 2],
[5, 6, 4, 7]]
Output : lt = [[4, 7, 5],
[5, 1, 6],
[3, 8, 4],
[9, 2, 7]]
Method #1: Using loops
Python
# Python program to get transpose# elements of two dimension listdef transpose(l1, l2): # iterate over list l1 to the length of an item for i in range(len(l1[0])): # print(i) row =[] for item in l1: # appending to new list with values and index positions # i contains index position and item contains values row.append(item[i]) l2.append(row) return l2# Driver codel1 = [[4, 5, 3, 9], [7, 1, 8, 2], [5, 6, 4, 7]]l2 = []print(transpose(l1, l2)) |
[[4, 7, 5], [5, 1, 6], [3, 8, 4], [9, 2, 7]]
Time Complexity: O(n*n) where n is the number of elements in the dictionary. The loops is used to perform the task and it takes O(n*n) time.
Auxiliary Space: O(1) constant additional space is required
Method #2: Using List comprehensions
Python
# Python program to get transpose# elements of two dimension listdef transpose(l1, l2): # we have nested loops in comprehensions # value of i is assigned using inner loop # then value of item is directed by row[i] # and appended to l2 l2 =[[row[i] for row in l1] for i in range(len(l1[0]))] return l2# Driver codel1 = [[4, 5, 3, 9], [7, 1, 8, 2], [5, 6, 4, 7]]l2 = []print(transpose(l1, l2)) |
[[4, 7, 5], [5, 1, 6], [3, 8, 4], [9, 2, 7]]
Time complexity: The nested loop used in the list comprehension has a time complexity of O(n^2) where n is the size of the input list
Auxiliary space: The space used in the function is the space required to create a new list l2, which is the size of the input list l1 in reverse order.
Method #3: Using numpy
Python3
# Python program to get transpose# elements of two dimension listimport numpy l1= [[4, 5, 3, 9], [7, 1, 8, 2], [5, 6, 4, 7]]print(numpy.transpose(l1)) |
Output:
[[4 7 5] [5 1 6] [3 8 4] [9 2 7]]
Method #4: Using zip function
Python
# Python program to get transpose# elements of two dimension listdef transpose(l1, l2): # star operator will first # unpack the values of 2D list # and then zip function will # pack them again in opposite manner l2 = list(map(list, zip(*l1))) return l2# Driver codel1 = [[4, 5, 3, 9], [7, 1, 8, 2], [5, 6, 4, 7]]l2 = []print(transpose(l1, l2))# code contributed by# chaudhary_19# Mayank Chaudhary# modified by Chirag Shilwant |
[[4, 7, 5], [5, 1, 6], [3, 8, 4], [9, 2, 7]]
