add level order tree construction and traversal implementation

Author: Adityasinghvats

24binarytree/05treeFromLevelNodes.cpp

@@ -0,0 +1,56 @@
+#include<iostream>
+#include<queue>
+#include<vector>
+//using level order traversal coonstruct a tree
+using namespace std;
+class Node{
+    public:
+    int val;
+    Node* left;
+    Node* right;
+    Node(int val){
+        this->val = val;
+        this->left = nullptr;
+        this->right = nullptr;
+    }
+};
+void levelOrderQueue(Node *root){
+    queue<Node*> q;
+    q.push(root);
+    while(q.size()>0){
+        Node* temp = q.front();
+        q.pop();
+        cout<<temp->val<<" ";
+        if(temp->left!=nullptr) q.push(temp->left);
+        if(temp->right!=nullptr) q.push(temp->right);
+    }
+    cout<<endl;
+}
+int main(){
+    queue<Node*> q;
+    vector<int> v = {1,2,3,4,5,INT_MIN,6,INT_MIN,INT_MIN,7,8,9,INT_MIN,INT_MIN,11}; //INT_MIN is used to represent NULL
+    Node* root = new Node(v[0]);
+    q.push(root);
+    int i = 1,j = 2;
+    while(i<v.size()){
+        Node* temp = q.front();
+        q.pop();
+        if(v[i]!=INT_MIN){//non null value
+            temp->left = new Node(v[i]);
+            q.push(temp->left);
+        }else {//for null value or INT_MIN though by default it will have nullptr
+            temp->left = nullptr;
+        }
+        if(v[j]!=INT_MIN && j<v.size()){//non null value
+            temp->right = new Node(v[j]);
+            q.push(temp->right);
+        }
+        else {//for null value or INT_MIN though by default it will have nullptr
+            temp->right = nullptr;
+        }
+        i+=2;
+        j+=2;
+    }
+    levelOrderQueue(root);
+    return 0;
+}