Trees-2 completed

ConstructBTFromInorderAndPostorder.cpp

@@ -0,0 +1,42 @@
+/**
+ * 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:
+    unordered_map<int, int> um;
+    int postIndex;
+    TreeNode* helper(vector<int>& postorder, int left, int right) {
+        if (left > right) {
+            return nullptr;
+        }
+
+        TreeNode *root = new TreeNode(postorder[postIndex]);
+        postIndex--;
+
+        int rootIndex = um[root->val];
+
+        root->right = helper(postorder, rootIndex+1, right);
+        root->left = helper(postorder, left, rootIndex-1);
+
+        return root;
+    }
+
+    TreeNode* buildTree(vector<int>& inorder, vector<int>& postorder) {
+        for (int i=0;i<inorder.size();i++){
+            um[inorder[i]]=i;
+        }
+        this->postIndex = inorder.size()-1;
+
+        int left = 0;
+        int right = inorder.size()-1;
+        return helper(postorder, left, right);
+    }
+};

SumRootToLeaf.cpp

@@ -0,0 +1,36 @@
+/**
+ * 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:
+    vector<string> answer;
+    int sumNumbers(TreeNode* root) {
+        helper(root, "");
+        int result=0;
+        for (string s:answer) {
+            result+= std::stoi(s);
+        }
+        return result;
+    }
+
+    void helper(TreeNode* root, string currSum) {
+        if (root == NULL) return;
+
+        if (root->left == NULL && root->right == NULL) {
+            currSum+=std::to_string(root->val);
+            answer.push_back(currSum);
+        }
+        currSum+=std::to_string(root->val);
+
+        helper(root->left, currSum);
+        helper(root->right, currSum);
+    }
+};