Merge pull request Ragnarok1023#18 from NotAdi/main

Data Structures/ Tree

Author: Ragnarok1023

C++/Data Structure/leetcode_623.cpp

@@ -0,0 +1,43 @@
+//this is the solution for problem no 623 on leetcode.
+//the solution uses BFS
+//https://leetcode.com/problems/add-one-row-to-tree/
+
+class Solution {
+public:
+    TreeNode* addOneRow(TreeNode* root, int val, int depth) {
+        if(root==NULL) return root;
+        int ld=0; //to store the local depth
+        queue<TreeNode*> q; //a queue for performing BFS
+        if(depth==1){ // checking edge cases
+            TreeNode* newroot= new TreeNode(val);
+            newroot->left=root;
+            newroot->right=NULL;
+            return newroot;
+        }
+        q.push(root);
+        while(!q.empty()){
+            ++ld; // after each iteration, our local depth increases by one
+            int sz= q.size(); 
+            //standard bfs template
+            for(int i=0;i<sz;i++){
+                TreeNode* temp= q.front();
+                q.pop();
+                if(ld==depth-1){ // checking if this is the depth after which we have to insert new nodes
+                    TreeNode* newl= new TreeNode(val);
+                    if(temp->left)  newl->left= temp->left;  // if current node is not the last, then assign the left subtree to new node
+                    temp->left= newl;
+                    TreeNode* newr= new TreeNode(val);
+                    if(temp->right) newr->right= temp->right;
+                    temp->right= newr;
+                }
+                if(temp->left)
+                    q.push(temp->left);
+                if(temp->right)
+                    q.push(temp->right);
+            }
+            if(ld==depth-1)
+                return root; //to save processing time because once roots inserted, no need to change anything in tree
+        }
+        return root;
+    }
+};