Added 3 solutions

varunu28 · varunu28 · commit 292033dca56a · 2019-07-13T09:41:37.000-07:00
diff --git a/Easy/Number of Days in a Month.java b/Easy/Number of Days in a Month.java
@@ -0,0 +1,24 @@
+class Solution {
+    public int numberOfDays(int Y, int M) {
+        int[] arr = {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
+        if (M == 2) {
+            return isLeapYear(Y) ? arr[M - 1] + 1 : arr[M - 1];
+        }
+
+        return arr[M- 1];
+    }
+
+    private boolean isLeapYear (int y) {
+        if (y % 4  == 0) {
+            if (y % 100 == 0) {
+                return y % 400 == 0;
+            }
+            else {
+                return true;
+            }
+        }
+        else {
+            return false;
+        }
+    }
+}
diff --git a/Easy/Remove Vowels from a String.java b/Easy/Remove Vowels from a String.java
@@ -0,0 +1,14 @@
+class Solution {
+    public String removeVowels(String S) {
+        StringBuilder sb = new StringBuilder();
+        Set<Character> set = new HashSet<>(Arrays.asList('a', 'e', 'i', 'o', 'u'));
+        
+        for (char c : S.toCharArray()) {
+            if (!set.contains(c)) {
+                sb.append(c);
+            }
+        }
+        
+        return sb.toString();
+    }
+}
diff --git a/Medium/Maximum Average Subtree.java b/Medium/Maximum Average Subtree.java
@@ -0,0 +1,62 @@
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode(int x) { val = x; }
+ * }
+ */
+class Solution {
+    Map<TreeNode, Integer> sumMap = new HashMap<>();
+    Map<TreeNode, Integer> numNodesMap = new HashMap<>();
+    double maxAvg = -1.0;
+    public double maximumAverageSubtree(TreeNode root) {
+        dfs(root);
+        return maxAvg;
+    }
+    
+    private void dfs(TreeNode root) {
+        if (root == null) {
+            return;
+        }
+        
+        int sum = getSum(root);
+        int nodes = getNumOfNodes(root);
+        
+        maxAvg = Math.max(maxAvg, ((double) (sum) / nodes));
+        
+        dfs(root.left);
+        dfs(root.right);
+    }
+    
+    private int getSum(TreeNode root) {
+        if (root == null) {
+            return 0;
+        }
+        
+        if (sumMap.containsKey(root)) {
+            return sumMap.get(root);
+        }
+        
+        int sum = root.val + getSum(root.left) + getSum(root.right);
+        sumMap.put(root, sum);
+        
+        return sum;
+    }
+    
+    private int getNumOfNodes(TreeNode root) {
+        if (root == null) {
+            return 0;
+        }
+        
+        if (numNodesMap.containsKey(root)) {
+            return numNodesMap.get(root);
+        }
+        
+        int numNodes = 1 + getNumOfNodes(root.left) + getNumOfNodes(root.right);
+        numNodesMap.put(root, numNodes);
+        
+        return numNodes;
+    }
+}
