Added solutions

Author: avidLearnerInProgress

find_mode_binary_search_tree.cpp

@@ -0,0 +1,33 @@
+/**
+ * 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:
+    int getModeCount(TreeNode* root, unordered_map<int, int> &umap){
+        if(root == NULL) return 0;
+        umap[root->val]++;
+        return max(umap[root->val], max(getModeCount(root->left, umap), getModeCount(root->right, umap))); 
+
+        //max of max..
+        //get mode count from map..
+        //find the pair in map with mc = modecount and then append all the node->data with same mc to the result vector
+    }
+    
+    vector<int> findMode(TreeNode* root) {
+        unordered_map<int, int> umap; //unordered because we dont need order :p
+        vector<int> result;
+        
+        int modeCount = getModeCount(root, umap);
+        for(auto it : umap){
+            if(it.second == modeCount)
+                result.push_back(it.first);
+        }
+        return result;
+    }
+};

reverse_level_order_traversal.cpp

@@ -0,0 +1,31 @@
+/**
+ * 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:
+    vector<vector<int>> result;
+    
+    void BFS(TreeNode *root, int level){
+        if(root == NULL) return;
+        
+        if(level == result.size()) result.push_back(vector<int>());
+        
+        result[level].push_back(root->val);
+        
+        BFS(root->left, level + 1);
+        BFS(root->right, level  + 1);
+        
+    }
+    vector<vector<int>> levelOrderBottom(TreeNode* root) {
+        
+        if(root == NULL) return vector<vector<int>>();
+        BFS(root, 0);
+        return vector<vector<int>> (result.rbegin(), result.rend());
+    }
+};