Create Diagonal sum in BST.java

Searching/Diagonal sum in BST.java

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+//Find the diagonal sum of a binary tree
+import java.util.HashMap;
+import java.util.Map;
+
+// A class to store a binary tree node
+class Node
+{
+    int data;
+    Node left = null, right = null;
+
+    Node(int data) {
+        this.data = data;
+    }
+}
+
+class Main
+{
+    // Recursive function to perform preorder traversal on the tree and
+    // fill the map with the diagonal sum of elements
+    public static void diagonalSum(Node root, int diagonal, Map<Integer, Integer> map)
+    {
+        // base case: empty tree
+        if (root == null) {
+            return;
+        }
+
+        // update the current diagonal with the node's value
+        map.put(diagonal, map.getOrDefault(diagonal, 0) + root.data);
+
+        // recur for the left subtree by increasing diagonal by 1
+        diagonalSum(root.left, diagonal + 1, map);
+
+        // recur for the right subtree with the same diagonal
+        diagonalSum(root.right, diagonal, map);
+    }
+
+    // Function to print the diagonal sum of a given binary tree
+    public static void diagonalSum(Node root)
+    {
+        // create an empty map to store the diagonal sum for every slope
+        Map<Integer, Integer> map = new HashMap<>();
+
+        // traverse the tree in a preorder fashion and fill the map
+        diagonalSum(root, 0, map);
+
+        // traverse the map and print the diagonal sum
+        System.out.println(map.values());
+    }
+
+    public static void main(String[] args)
+    {
+        /* Construct the following tree
+                   1
+                 /   \
+                /     \
+               2       3
+              /      /  \
+             /      /    \
+            4      5      6
+                  / \
+                 /   \
+                7     8
+        */
+
+        Node root = new Node(1);
+        root.left = new Node(2);
+        root.right = new Node(3);
+        root.left.left = new Node(4);
+        root.right.left = new Node(5);
+        root.right.right = new Node(6);
+        root.right.left.left = new Node(7);
+        root.right.left.right = new Node(8);
+
+        diagonalSum(root);
+    }
+}