some logical improvements

src/com/dsa/trees/DepthFirstTraversal.java

@@ -24,7 +24,7 @@ public class DepthFirstTraversal {
                     queue.offer(node.left);
                 }
                 index++;
-                if (!elements[index].equalsIgnoreCase("null")) {
+                if (index < elements.length && !elements[index].equalsIgnoreCase("null")) {
                     node.right = new TreeNode(Integer.parseInt(elements[index]));
                     queue.offer(node.right);
                 }
@@ -43,27 +43,33 @@ public class DepthFirstTraversal {
     }
 
     private static int diameter = 0;
+
     public static int diameterOfBinaryTree(TreeNode root) {
         diameter = 0;
-        if (root == null) return 0;
+        if (root == null)
+            return 0;
         heightOfBT(root);
-        return diameter - 1;
+        return diameter;
     }
 
     public static int heightOfBT(TreeNode root) {
-        if (root == null) return 0;
+        if (root == null)
+            return 0;
         int leftHeight = heightOfBT(root.left);
         int rightHeight = heightOfBT(root.right);
-        diameter = Math.max(leftHeight + rightHeight + 1, diameter);
+        diameter = Math.max(leftHeight + rightHeight, diameter);
         return Math.max(leftHeight, rightHeight) + 1;
     }
 
     public static int minDepth(TreeNode root) {
-        if(root == null) return 0;
+        if (root == null)
+            return 0;
         int leftHeight = minDepth(root.left);
         int rightHeight = minDepth(root.right);
-        if (leftHeight == 0) return rightHeight + 1;
-        if (rightHeight == 0) return leftHeight + 1;
+        if (leftHeight == 0)
+            return rightHeight + 1;
+        if (rightHeight == 0)
+            return leftHeight + 1;
         return Math.min(leftHeight, rightHeight) + 1;
     }
 
@@ -72,28 +78,36 @@ public class DepthFirstTraversal {
     }
 
     public static int balancedDepth(TreeNode root) {
-        if (root == null) return 0;
+        if (root == null)
+            return 0;
         int leftHeight = balancedDepth(root.left);
         int rightHeight = balancedDepth(root.right);
-        if (leftHeight == -1 || rightHeight == -1) return -1;
+        if (leftHeight == -1 || rightHeight == -1)
+            return -1;
         int weight = Math.abs(leftHeight - rightHeight);
-        if (weight > 1) return -1;
+        if (weight > 1)
+            return -1;
         return Math.max(leftHeight, rightHeight) + 1;
     }
 
     public static boolean hasPathSum(TreeNode root, int targetSum) {
-        if(root == null) return false;
-        if (root.left == null && root.right == null && root.val == targetSum) return true;
+        if (root == null)
+            return false;
+        if (root.left == null && root.right == null && root.val == targetSum)
+            return true;
         int requiredNewSum = targetSum - root.val;
         boolean hasPathSumLeft = hasPathSum(root.left, requiredNewSum);
-        if (hasPathSumLeft) return true;
+        if (hasPathSumLeft)
+            return true;
         return hasPathSum(root.right, requiredNewSum);
     }
 
     private static List<Integer> pathTracer = new LinkedList<>();
     private static List<List<Integer>> allPaths = new LinkedList<>();
+
     public static List<List<Integer>> pathSum(TreeNode root, int targetSum) {
-        if (root == null) return allPaths;
+        if (root == null)
+            return allPaths;
         pathTracer.add(root.val);
         if (root.left == null && root.right == null && root.val == targetSum) {
             allPaths.add(new LinkedList<>(pathTracer));
@@ -106,18 +120,23 @@ public class DepthFirstTraversal {
     }
 
     private static int maxSum;
+
     public static int maxPathSum(TreeNode root) {
-        if (root != null) maxSum = root.val;
+        if (root != null)
+            maxSum = root.val;
         int maxSumInternal = maxPathSumInternal(root);
         return Math.max(maxSumInternal, maxSum);
     }
 
     private static int maxPathSumInternal(TreeNode root) {
-        if (root == null) return 0;
+        if (root == null)
+            return 0;
         int leftMaxSum = maxPathSumInternal(root.left);
         int rightMaxSum = maxPathSumInternal(root.right);
         maxSum = Math.max(leftMaxSum + rightMaxSum + root.val, maxSum); // is max including current node in path
-        int pathMax = Math.max(leftMaxSum + root.val, Math.max(rightMaxSum + root.val, root.val)); //for moving up just return one of max sum to parent
+        int pathMax = Math.max(leftMaxSum + root.val, Math.max(rightMaxSum + root.val, root.val)); // for moving up just
+        // return one of max
+        // sum to parent
         maxSum = Math.max(pathMax, maxSum);
         return pathMax;
     }