Added serialize and deserialize binary tree problem

Author: Karnika06

Codechef Problems/MaximumArrayXOR.java

@@ -0,0 +1,88 @@
+/*
+Implementation of Serialize and Deserialize Binary Tree
+
+According to the problem:
+We need to ensure that a binary tree can be serialized to a string and this string 
+can be deserialized to the original tree structure.
+
+NOTE:Serialization is the process of converting a data structure or object into a sequence of 
+bits so that it can be stored in a file or memory buffer, or transmitted across a network 
+connection link to be reconstructed later in the same or another computer environment.
+
+Link to the problem: https://leetcode.com/problems/serialize-and-deserialize-binary-tree/
+*/
+
+/*
+Input: root = [1,2,3,null,null,4,5]
+Output: [1,2,3,null,null,4,5]
+*/
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
+ * };
+ */
+class Codec {
+           TreeNode* makeTree(queue<string> &q) {
+        string s = q.front();
+        q.pop();
+        if(s=="null")
+            return NULL;
+        TreeNode* root = new TreeNode(stoi(s));
+        root->left = makeTree(q);
+        root->right = makeTree(q);
+        return root;
+    }
+public:
+
+    // Encodes a tree to a single string.
+    string serialize(TreeNode* root) {
+        if(!root)
+            return "null,";
+      return to_string(root->val)+","+ serialize(root->left) + serialize(root->right);
+    }
+
+    // Decodes your encoded data to tree.
+    TreeNode* deserialize(string data) {
+        string s ="";
+        queue <string> q;
+        for(char c: data) {
+            if(c ==',') {
+                q.push(s);
+                s="";
+                continue;
+            }
+            s+=c;
+        }
+        return makeTree(q);
+    }
+} 
+
+/*
+Time complexity: O(n)
+
+Test cases:
+
+Example 1:
+
+Input: root = [1,2,3,null,null,4,5]
+Output: [1,2,3,null,null,4,5]
+
+Example 2:
+
+Input: root = []
+Output: []
+
+Example 3:
+
+Input: root = [1]
+Output: [1]
+
+Example 4:
+
+Input: root = [1,2]
+Output: [1,2]
+*/