Create 2415. Reverse Odd Levels of Binary Tree (#667)

Author: Chayandas07

2415. Reverse Odd Levels of Binary Tree

@@ -0,0 +1,46 @@
+class Solution {
+public:
+    TreeNode* reverseOddLevels(TreeNode* root) {
+        // we are given a perfect binary tree;
+        vector<TreeNode*> prev;
+        vector<TreeNode*> next;
+        queue<TreeNode*> q;
+        next.push_back(root);
+        q.push(root);
+        int lvl = 0;
+        while(next.empty() == false) {
+            // for(TreeNode* i : prev) cout<<i->val<<" ";
+            // cout<<endl;
+            // for(TreeNode* i : next) cout<<i->val<<" ";
+            // cout<<endl;
+            int index = 0;
+            if (lvl & 1) 
+                reverse(next.begin(),next.end());
+
+            for(TreeNode* i:prev) {
+                i->left = next[index];
+                i->right = next[index + 1];
+                index += 2;
+            }
+
+            lvl+=1;
+            prev = next;
+            vector<TreeNode*> temp;
+            int q_size = q.size();
+            while(q_size--) {
+                TreeNode* front = q.front();
+                q.pop();
+                if (front -> left != NULL) {
+                    temp.push_back(front->left);
+                    q.push(front->left);
+                }
+                if (front -> right != NULL) {
+                    temp.push_back(front->right);
+                    q.push(front->right);
+                }
+            }
+            next = temp;
+        }
+        return root;
+    }
+};