Added to Trees

Author: sr-sweta

Data Structures/Trees/Flatten_BinaryTree_to_LinkedList.cpp

@@ -0,0 +1,52 @@
+/*
+Src : LeetCode
+--------------
+
+Given the root of a binary tree, flatten the tree into a "linked list":
+
+1) The "linked list" should use the same TreeNode class where the right child pointer points to the next node in the list and the left child pointer is always null.
+2) The "linked list" should be in the same order as a pre-order traversal of the binary tree.
+
+Input: root = [1,2,5,3,4,null,6]
+Output: [1,null,2,null,3,null,4,null,5,null,6]
+*/
+
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+public:
+    TreeNode* flattenSubtrees(TreeNode* root){
+        if(!root->left && !root->right) return root;
+        if(root->left==NULL)
+            return fun(root->right);
+        TreeNode* last=fun(root->left);
+        last->right=root->right;
+        root->right=root->left;
+        root->left=NULL;
+        return fun(last);
+    }
+    
+    void flatten(TreeNode* root) {
+        if(!root) return;
+        flatten(root->left);
+        flatten(root->right);
+        TreeNode* right=root->right;
+        root->right=root->left;
+        root->left=NULL;
+        TreeNode* cur=root;
+        while(cur->right){
+            cur=cur->right;
+        }
+        cur->right=right;
+        
+    }
+};