Given a nested list, the task is to write a python program to flatten a nested list using recursion.
Examples:
Input: [[8, 9], [10, 11, ‘geeks’], [13]]
Output: [8, 9, 10, 11, ‘geeks’, 13]
Input: [[‘A’, ‘B’, ‘C’], [‘D’, ‘E’, ‘F’]]
Output: [‘A’, ‘B’, ‘C’, ‘D’, ‘E’, ‘F’]
Step-by-step Approach:
- Firstly, we try to initialize a variable into the linked list.
- Then, our next task is to pass our list as an argument to a recursive function for flattening the list.
- In that recursive function, if we find the list as empty then we return the list.
- Else, we call the function in recursive form along with its sublists as parameters until the list gets flattened.
- Then finally, we will print the flattened list as output.
Below are some python programs based on the above approach:
Example 1:
Python3
def flattenList[nestedList]:
if not[bool[nestedList]]:
return nestedList
if isinstance[nestedList[0], list]:
return flattenList[*nestedList[:1]] + flattenList[nestedList[1:]]
return nestedList[:1] + flattenList[nestedList[1:]]
nestedList =
[[8, 9], [10, 11, 'geeks'], [13]]
print['Nested List:\n', nestedList]
print["Flattened List:\n", flattenList[nestedList]]
Output:
Nested List: [[8, 9], [10, 11, 'geeks'], [13]] Flattened List: [8, 9, 10, 11, 'geeks', 13]
Example 2:
Python3
def flattenList[nestedList]:
if not[bool[nestedList]]:
return nestedList
if
isinstance[nestedList[0], list]:
return flattenList[*nestedList[:1]] + flattenList[nestedList[1:]]
return nestedList[:1] + flattenList[nestedList[1:]]
nestedList = [['A', 'B', 'C'], ['D', 'E', 'F']]
print['Nested List:\n', nestedList]
print["Flattened List:\n", flattenList[nestedList]]
Output:
Nested List: [['A', 'B', 'C'], ['D', 'E', 'F']] Flattened List: ['A', 'B', 'C', 'D', 'E', 'F']
Example 3:
Python3
def flattenList[nestedList]:
if not[bool[nestedList]]:
return nestedList
if isinstance[nestedList[0], list]:
return flattenList[*nestedList[:1]] + flattenList[nestedList[1:]]
return nestedList[:1] + flattenList[nestedList[1:]]
nestedList =
[[1], [2], [3], [4], [5]]
print['Nested List:\n', nestedList]
print["Flattened List:\n", flattenList[nestedList]]
Output:
Nested List: [[1], [2], [3], [4], [5]] Flattened List: [1, 2, 3, 4, 5]