Added some Easy questions 🎉

Author: Jatin-8898

Easy/BalancedBinaryTree.java

@@ -0,0 +1,35 @@
+public class TreeNode {
+    int val;
+    TreeNode left;
+    TreeNode right;
+    TreeNode(int x) { val = x; }
+}
+class Solution {
+  
+  public boolean isBalanced(TreeNode root) {
+      int left;
+      int right;
+      
+      if(root == null)
+          return true;
+      
+      left = height(root.left);
+      right = height(root.right);
+      
+      if(Math.abs(left-right) <=1 && isBalanced(root.left) && isBalanced(root.right))
+          return true;
+      
+      return false;
+  }
+  
+  int height(TreeNode node) 
+  { 
+      /* base case tree is empty */
+      if (node == null) 
+          return 0; 
+
+      /* If tree is not empty then height = 1 + max of left 
+       height and right heights */
+      return 1 + Math.max(height(node.left), height(node.right)); 
+  } 
+}

Easy/StockBuySell.java renamed to Easy/BestTimeToBuyAndSellStock.java

@@ -1,4 +1,4 @@
-class StockBuySell {
+class Solution {
     public static void main(String[] args) {
         int[] arr = {7,1,5,3,6,4};
         System.out.println(maxProfit(arr));

Easy/ConvertSortedArrayToBinarySearchTree.java

@@ -0,0 +1,40 @@
+class TreeNode {
+    int val;
+    TreeNode left;
+    TreeNode right;
+    TreeNode(int x) { val = x; }
+}
+class ConvertSortedArrayToBinarySearchTree {
+
+    public static void main(String[] args) {
+        int[] nums = {-10,-3,0,5,9};
+        TreeNode head = sortedArrayToBST(nums);
+        System.out.println(head.val);
+        /*System.out.println(head.val);
+        System.out.println(head.left.val);
+        System.out.println(head.left.right.val);
+        System.out.println(head.right.val);
+        System.out.println(head.right.right.val);
+        */
+    }
+
+    public static TreeNode sortedArrayToBST(int[] nums) {
+        if(nums.length == 0) 
+            return null;
+            
+        return buildBST(nums, 0, nums.length - 1);
+    }
+    
+    public static  TreeNode buildBST(int[] nums, int start, int end) {
+        if(start > end) 
+            return null;
+
+        int mid = start + (end - start) / 2;
+        TreeNode root = new TreeNode(nums[mid]);
+        
+        root.left = buildBST(nums, start, mid - 1);
+        root.right = buildBST(nums, mid + 1, end);
+        
+        return root;
+    }
+}

Easy/CountAndSay.class

@@ -0,0 +1,14 @@
+class Solution {
+    public int titleToNumber(String s) {
+        
+        int result  = 0;
+        
+        for (int i = 0; i < s.length(); i++){   //for s = A => 65-65=0 => Add 1 to it
+    
+            result *= 26;                       //For AA = 1*26 = 26 + 1 = 27
+            result += ((s.charAt(i) - 'A') + 1);    
+        }
+    
+        return result;
+    }
+}

Easy/DistributeCandies.class

@@ -0,0 +1,10 @@
+class Solution{
+    
+    public int trailingZero(int n) { //Eg 25
+    
+        return n == 0   ? 0 :    (n/2 +  trailingZero(n/2));
+        
+        //25/2 = 5 + (25/2)     =>    5 + 1 = 6
+    
+    }
+}

Easy/ExcelSheetColumnNumber.java

@@ -1,25 +1,5 @@
 class Solution {
 
-    /* BEST SOLUTION 
-        TIME : O(n)
-        SPACE: O(1)
-    */
-    public int robEff(int[] nums) {
-        if (nums.length == 0) return 0;
-        
-        int prev1 = 0;
-        int prev2 = 0;
-        
-        for (int num : nums) {
-            int tmp = prev1;
-            prev1 = Math.max(prev2 + num, prev1);
-            prev2 = tmp;
-        }
-        
-        return prev1;
-    }
-
-    /* ANOTHER WAY */
     public int rob(int[] nums) {    //Eg 2, 7 ,9 ,3 ,1 
 
         int n = nums.length;        //n=5
@@ -39,7 +19,6 @@ public int rob(int[] nums) {    //Eg 2, 7 ,9 ,3 ,1
         return Math.max(nums[n-1], nums[n-2]);  //Max(12,10)  => return 12 correct ans
     }
 
-
     /* ANOTHER APPROACH */
     public int rob2(int[] nums) {
         if (nums.length == 0) return 0;