Added day01 and day02 solutions

Author: avidLearnerInProgress

30-days-of-code-july/01.arrangeCoins.cpp

@@ -0,0 +1,15 @@
+class Solution {
+public:
+    int arrangeCoins(int n) {
+        long start = 0, end = n;
+        long k, curr;
+        while(start <= end) {
+            k = start + (end - start) / 2;
+            curr = k * (k + 1) / 2;
+            if(curr == n) return (int) k;
+            if(n < curr) end = k - 1;
+            else start = k + 1;
+        }
+        return (int)end;
+    }
+};

30-days-of-code-july/02.levelOrderTraversal-II.cpp

@@ -0,0 +1,53 @@
+/**
+ * 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());
+        
+        queue<TreeNode *> q;
+        q.push(root);
+        
+        vector<int> clevel;
+        vector<vector<int>> alevel;
+        
+        while(!q.empty()){
+            int sz = q.size();
+            while(sz--){
+                TreeNode *curr = q.front();
+                q.pop();
+                clevel.push_back(curr->val);
+                if(curr->left)
+                    q.push(curr->left);
+                if(curr->right)
+                    q.push(curr->right);
+            }
+            alevel.push_back(clevel);
+            clevel.clear();
+        }
+        return vector<vector<int>> (alevel.rbegin(), alevel.rend());
+    }
+};