N Ary Tree Postorder Traversal - Leetcode Solution

The problem statement for N Ary Tree Postorder Traversal on leetcode is as follows:

"Given the root of an n-ary tree, return the postorder traversal of its nodes' values."

In simple terms, we have to traverse an n-ary tree in a postorder fashion and return the values of the nodes in that order.

Solution:

To solve the N Ary Tree Postorder Traversal problem, we can use a recursive approach. We start by visiting all the children of a node in a postorder fashion, then we visit the node itself. We continue this process for all nodes of the tree.

Algorithm:

1. If the root is empty, return an empty list.

2. Define a function, "postorder," that takes the root of the tree as an input.

3. Initialize an empty list "result" that will store the postorder traversal of the tree.

4. Loop through each child of the current node in a postorder fashion:

    a. Recursively call the "postorder" function on the child, and append the output to the "result" list.
   

5. Append the value of the root node to the "result" list.

6. Return the "result" list.

Python Code:

Below is the implementation of the above algorithm in Python:

class TreeNode: def init(self, val=None, children=None): self.val = val self.children = children

def postorder(root: TreeNode): if not root: return [] result = [] for child in root.children: result += postorder(child) result.append(root.val) return result

Complexity Analysis:

The time complexity of the above algorithm is O(n), where n is the number of nodes in the n-ary tree. We traverse each node once, and the time taken to visit a node is constant.

The space complexity of the algorithm is also O(n), as we use a list "result" to store the postorder traversal of the tree. In the worst case, when the tree is linear like a linked list, the space complexity will be O(n).

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