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N-ary Tree Preorder Traversal in C++
Suppose we have one n-ary tree, we have to find the preorder traversal of its nodes.
So, if the input is like
then the output will be [1,3,5,6,2,4]
To solve this, we will follow these steps −
Define an array ans
Define a method called preorder(), this will take root
if root is null, then −
return empty list
insert value of root at the end of ans
for all child i in children array of root
preorder(i)
return ans
Example
Let us see the following implementation to get a better understanding −
#include <bits/stdc++.h> using namespace std; void print_vector(vector<auto> v){ cout << "["; for(int i = 0; i<v.size(); i++){ cout << v[i] << ", "; } cout << "]"<<endl; } class Node { public: int val; vector<Node*> children; Node() {} Node(int _val) { val = _val; } Node(int _val, vector<Node*> _children) { val = _val; children = _children; } }; class Solution { public: vector<int&g; ans; vector<int> preorder(Node* root) { if (!root) return {}; ans.emplace_back(root->val); for (auto i : root->children) preorder(i); return ans; } }; main(){ Solution ob; Node *node5 = new Node(5), *node6 = new Node(6); vector<Node*> child_of_3 = {node5, node6}; Node* node3 = new Node(3, child_of_3); Node *node2 = new Node(2), *node4 = new Node(4);l vector<Node*> child_of_1 = {node3, node2, node4}; Node *node1 = new Node(1, child_of_1); print_vector(ob.preorder(node1)); }
Input
Node *node5 = new Node(5), *node6 = new Node(6); vector<Node*> child_of_3 = {node5, node6}; Node* node3 = new Node(3, child_of_3); Node *node2 = new Node(2), *node4 = new Node(4); vector<Node*> child_of_1 = {node3, node2, node4}; Node *node1 = new Node(1, child_of_1);
Output
[1, 3, 5, 6, 2, 4, ]
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