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This approach utilizes recursion to traverse the N-ary tree in a postorder fashion. For each node, we recursively visit all its children first before processing the node itself.
Time Complexity: O(n), where n is the number of nodes, as each node is visited once.
Space Complexity: O(n) for the recursion stack in the worst case (maximum tree height).
1function Node(val, children) {
2 this.val = val;
3 this.children = children || [];
4}
5
6var postorder = function(root) {
7 const result = [];
8 function traverse(node) {
9 if (node === null) return;
10 for (let child of node.children) {
11 traverse(child);
12 }
13 result.push(node.val);
14 }
15 traverse(root);
16 return result;
17};
18JavaScript follows a similar recursive approach. The function traverse handles node traversal and updates the result array with node values after processing all child nodes. The main function postorder executes the traversal, starting from root, and returns the final result.
This approach uses an iterative method to perform postorder traversal with the help of a stack to simulate recursion. Nodes are pushed onto the stack in such a way that their children are processed before the node itself.
Time Complexity: O(n)
Space Complexity: O(n)
1import
In Java, we manage the postorder traversal with a stack and a linked list to prepend node values. Nodes are pushed onto the stack, processed by visiting children first, and added to the list in reverse order. The use of addFirst ensures that the values appear in postorder upon completion.