Python Program to Find the Total Sum of a Nested List Using Recursion
A nested list is given. The task is to print the sum of this list using recursion. A nested list is a list whose elements can also be a list.
Examples :
Input: [1,2,[3]] Output: 6 Input: [[4,5],[7,8,[20]],100] Output: 144 Input: [[1,2,3],[4,[5,6]],7] Output: 28
Recursion: In recursion, a function calls itself repeatedly. This technique is generally used when a problem can be divided into smaller subproblems of the same form.
Implementation:
Iterate through the list and whenever we find that an element of the list is also a list that means we have to do the same task of finding the sum with this element list (which can be nested) as well. So we have found a subproblem and, we can call the same function to perform this task and just change the argument to this sublist. And when the element is not a list, then simply add its value to the global total variable.
Python3
# Python Program to find sum# of nested list using Recursiondef sum_nestedlist( l ): # specify that global variable is # referred to here in this function total = 0 for j in range(len(l)): if type(l[j]) == list : # call the same function if # the element is a list total+= sum_nestedlist(l[j]) else: # if it's a single element # and not a list, add it to total total += l[j] return total print(sum_nestedlist([[1,2,3],[4,[5,6]],7])) |
28
Time Complexity: O(N), Where N is the total number of elements in the list.
Auxiliary Space: O(1)
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