Convert BST to Greater Tree

ConvertBSTToGreaterTree.cpp

@@ -0,0 +1,69 @@
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
+ * };
+ */
+class Solution {
+public:
+    void inorder(TreeNode* root, vector<int>& in){
+        if(!root){
+            return;
+        }
+        inorder(root->left, in);
+        in.push_back(root->val);
+        inorder(root->right, in);
+    }
+
+    int find(vector<int>& in, int key){
+        int start = 0, end = in.size()-1;
+
+        while(start <= end){
+            int mid = start + (end-start)/2;
+            if(in[mid] == key){
+                return mid;
+            }
+            else if(in[mid] > key){
+                end = mid-1;
+            }
+            else{
+                start = mid+1;
+            }
+        }
+
+        return -1;
+    }
+
+    TreeNode* make(TreeNode* root, vector<int>& in, vector<int>& sumV){
+        if(!root){
+            return NULL;
+        }
+
+        int index = find(in, root->val);
+        root->val = sumV[index];
+
+        root->left = make(root->left, in, sumV);
+        root->right = make(root->right, in, sumV);
+
+        return root;
+    }
+
+    TreeNode* convertBST(TreeNode* root) {
+        vector<int> in;
+        inorder(root, in);
+
+        vector<int> sumV(in.size(), 0);
+
+        int sum = 0;
+
+        for(int i = in.size()-1; i >= 0; i--){
+            sum += in[i];
+            sumV[i] = sum;
+        }
+
+        return make(root, in, sumV);
+    }
+};