Create main.cpp

Author: JawadSher

18 - Binary Search Tree Data Structure Problems/15 - Balance a Binary Search Tree/main.cpp

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+/**
+ * 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:
+    void inOrder(TreeNode* root, vector<TreeNode*> &inOrderValues){
+        if(root == NULL) return;
+
+        inOrder(root -> left, inOrderValues);
+        inOrderValues.push_back(root);
+        inOrder(root -> right, inOrderValues);
+    }
+
+    TreeNode* inorderToBST(int start, int end, vector<TreeNode*> &inOrderValues){
+        if(start > end) return NULL;
+
+        int mid = start + (end - start) / 2;
+
+        TreeNode* root = inOrderValues[mid];
+
+        root -> left = inorderToBST(start, mid-1, inOrderValues);
+        root -> right = inorderToBST(mid + 1, end, inOrderValues);
+
+        return root;
+    }
+    TreeNode* balanceBST(TreeNode* root) {
+        vector<TreeNode*> inOrderValues;
+        inOrder(root, inOrderValues);
+
+        return inorderToBST(0, inOrderValues.size()-1, inOrderValues);
+    }
+};