Rewrite UBS to use precomputed deltas and add deterministic demos

Searching-algorithms/Uniform_binarysearch.java

@@ -19,6 +19,7 @@ public static void main(String[] args) {
         }
         if (size == 0) {
             System.out.println("Nothing to sort/search");
+            runDeterministicDemo();
             sc.close();
             return;
         }
@@ -31,6 +32,7 @@ public static void main(String[] args) {
 
         if (!isSorted(arr)) {
             System.out.println("Invalid input: Uniform Binary Search requires a sorted array in non-decreasing order.");
+            runDeterministicDemo();
             sc.close();
             return;
         }
@@ -43,33 +45,68 @@ public static void main(String[] args) {
         } else {
             System.out.println("Element " + key + " was NOT Found in the entered Array.");
         }
+
+        runDeterministicDemo();
         sc.close();
     }
+
     public static int binunisearch(int[] arr, int key) {
         if (arr == null || arr.length == 0) {
             return -1;
         }
+
         int n = arr.length;
-        int k = (int)(Math.log(n) / Math.log(2));
-        System.out.println("n = " + n);
-        System.out.println("k = " + k);
-        int[] offset = new int[k + 1];
-        offset[0] = 1 << k;
-        for (int i = 1; i <= k; i++) {
-            offset[i] = offset[i-1] / 2;
-        }
-        int index = -1;
-        for (int i = 0; i <= k; i++) {
-            int next = index + offset[i];
-            if (next < n && arr[next] <= key) {
-                index = next;                  
-             }
+        int[] deltas = buildDeltaTable(n);
+        int probe = deltas[0] - 1; // center probe
+        probe = Math.max(0, Math.min(n - 1, probe));
+
+        for (int i = 0; i < deltas.length; i++) {
+            if (arr[probe] == key) {
+                return probe;
+            }
+
+            if (i == deltas.length - 1) {
+                break;
+            }
+
+            int move = deltas[i + 1];
+            if (key < arr[probe]) {
+                probe -= move;
+            } else {
+                probe += move;
+            }
+
+            // Keep the probe index within valid bounds.
+            probe = Math.max(0, Math.min(n - 1, probe));
         }
-        if (index >= 0 && arr[index] == key)
-            return index;
+
         return -1;
     }
 
+    private static int[] buildDeltaTable(int n) {
+        int[] temp = new int[32];
+        int count = 0;
+        int delta = (n + 1) / 2;
+
+        while (delta > 0) {
+            temp[count++] = delta;
+            delta /= 2;
+        }
+
+        return Arrays.copyOf(temp, count);
+    }
+
+    private static void runDeterministicDemo() {
+        int[] demoArr = {2, 5, 8, 12, 16, 23, 38, 56, 72, 91};
+        int foundKey = 23;
+        int notFoundKey = 24;
+
+        System.out.println("\nDeterministic UBS demonstration");
+        System.out.println("Demo array: " + Arrays.toString(demoArr));
+        System.out.println("Search key (found case) " + foundKey + " -> index: " + binunisearch(demoArr, foundKey));
+        System.out.println("Search key (not-found case) " + notFoundKey + " -> index: " + binunisearch(demoArr, notFoundKey));
+    }
+
     public static boolean isSorted(int[] arr) {
         if (arr == null || arr.length < 2) {
             return true;