Add nearest right neighbor (#2574)

DataStructures/Trees/nearestRightKey.java

@@ -0,0 +1,84 @@
+package DataStructures.NRKTrees;
+
+import java.util.Scanner;
+import java.util.concurrent.ThreadLocalRandom;
+
+class Main {
+
+    public static void main(String[] args) {
+        NRKTree root = BuildTree();
+        Scanner sc = new Scanner(System.in);
+        System.out.print("Enter first number: ");
+        int inputX0 = sc.nextInt();
+        int toPrint = nearestRightKey(root, inputX0);
+        System.out.println("Key: " + toPrint);
+    }
+
+    public static NRKTree BuildTree() {
+        int randomX = ThreadLocalRandom.current().nextInt(0, 100 + 1);
+        NRKTree root = new NRKTree(null, null, randomX);
+
+        for (int i = 0; i < 1000; i++) {
+            randomX = ThreadLocalRandom.current().nextInt(0, 100 + 1);
+            root = root.insertKey(root, randomX);
+        }
+
+        return root;
+    }
+
+    public static int nearestRightKey(NRKTree root, int x0) {
+        //Check whether tree is empty
+        if(root == null){
+           return 0;
+        }
+        else {
+            if(root.data - x0 > 0){
+                // Go left
+                int temp = nearestRightKey(root.left, x0);
+                if(temp == 0){
+                    return root.data;
+                }
+                return temp;
+            } else {
+                // Go right
+                return nearestRightKey(root.right, x0);
+            }
+
+        }
+    }
+
+}
+
+
+class NRKTree {
+
+    public NRKTree left;
+    public NRKTree right;
+    public int data;
+
+    public NRKTree(int x) {
+        this.left = null;
+        this.right = null;
+        this.data = x;
+    }
+
+    public NRKTree(NRKTree right, NRKTree left, int x) {
+        this.left = left;
+        this.right = right;
+        this.data = x;
+    }
+
+    public NRKTree insertKey(NRKTree current, int value) {
+        if (current == null) {
+            return new NRKTree(value);
+        }
+
+        if (value < current.data) {
+            current.left = insertKey(current.left, value);
+        } else if (value > current.data) {
+            current.right = insertKey(current.right, value);
+        }
+
+        return current;
+    }
+}