Harden binary-family searches against unsorted input

Searching-algorithms/Binarysearch.java

@@ -6,12 +6,19 @@ public static void main(String[] args) {
         Scanner sc = new Scanner(System.in);
         System.out.println("Enter the length of the Array: ");
         int size = sc.nextInt();
-        System.out.println("Enter Array elements: ");
+        System.out.println("Enter Array elements in non-decreasing (sorted) order: ");
         int arr[] = new int[size];
         for (int i = 0; i < size; i++) {
             arr[i] = sc.nextInt();
         }
         System.out.println("Entered Array: " + Arrays.toString(arr));
+
+        if (!isSorted(arr)) {
+            System.out.println("Invalid input: Binary Search requires a sorted array in non-decreasing order.");
+            sc.close();
+            return;
+        }
+
         System.out.println("Enter the key element to be Found: ");
         int key = sc.nextInt();
         int result = binarysearch(arr, key);
@@ -20,6 +27,7 @@ public static void main(String[] args) {
         } else {
             System.out.println("Element " + key + " was NOT Found in the entered Array.");
         }
+        sc.close();
     }
     public static int binarysearch(int[] arr, int key) {
         int low = 0; 
@@ -35,4 +43,13 @@ else if (key < arr[mid])
         }
         return -1;
     }
+
+    public static boolean isSorted(int[] arr) {
+        for (int i = 1; i < arr.length; i++) {
+            if (arr[i] < arr[i - 1]) {
+                return false;
+            }
+        }
+        return true;
+    }
 }

Searching-algorithms/Fibonaccisearch.java

@@ -9,13 +9,18 @@ public static void main(String[] args) {
         int size = sc.nextInt();
 
         int[] arr = new int[size];
-        System.out.println("Enter array elements: ");
+        System.out.println("Enter array elements in non-decreasing (sorted) order: ");
         for (int i = 0; i < size; i++) {
             arr[i] = sc.nextInt();
         }
 
-        Arrays.sort(arr);
-        System.out.println("Sorted Array: " + Arrays.toString(arr));
+        System.out.println("Entered Array: " + Arrays.toString(arr));
+
+        if (!isSorted(arr)) {
+            System.out.println("Invalid input: Fibonacci Search requires a sorted array in non-decreasing order.");
+            sc.close();
+            return;
+        }
 
         System.out.println("Enter the key element to be Found: ");
         int key = sc.nextInt();
@@ -67,4 +72,13 @@ public static int fibonaccisearch(int[] arr, int key) {
 
         return -1;
     }
+
+    public static boolean isSorted(int[] arr) {
+        for (int i = 1; i < arr.length; i++) {
+            if (arr[i] < arr[i - 1]) {
+                return false;
+            }
+        }
+        return true;
+    }
 }

Searching-algorithms/Interpolationsearch.java

@@ -6,12 +6,19 @@ public static void main(String[] args) {
         Scanner sc = new Scanner(System.in);
         System.out.println("Enter the length of the Array: ");
         int n = sc.nextInt();
-        System.out.println("Enter Array elements: ");
+        System.out.println("Enter Array elements in non-decreasing (sorted) order: ");
         int arr[] = new int[n];
         for (int i = 0; i < n; i++) {
             arr[i] = sc.nextInt();
         }
         System.out.println("Entered Array: " + Arrays.toString(arr));
+
+        if (!isSorted(arr)) {
+            System.out.println("Invalid input: Interpolation Search requires a sorted array in non-decreasing order.");
+            sc.close();
+            return;
+        }
+
         System.out.println("Enter the key element to be Found: ");
         int key = sc.nextInt();
         int result = interpolationSearch(arr, 0, arr.length - 1, key);
@@ -20,6 +27,7 @@ public static void main(String[] args) {
         } else {
             System.out.println("Element " + key + " was NOT Found in the entered Array.");
         }
+        sc.close();
     }
     public static int interpolationSearch(int arr[], int lo, int hi, int x) {
         int pos;
@@ -39,4 +47,13 @@ public static int interpolationSearch(int arr[], int lo, int hi, int x) {
         }
         return -1;     
     }
+
+    public static boolean isSorted(int[] arr) {
+        for (int i = 1; i < arr.length; i++) {
+            if (arr[i] < arr[i - 1]) {
+                return false;
+            }
+        }
+        return true;
+    }
 }

Searching-algorithms/Uniform_binarysearch.java

@@ -6,12 +6,19 @@ public static void main(String[] args) {
         Scanner sc = new Scanner(System.in);
         System.out.println("Enter the length of the Array: ");
         int size = sc.nextInt();
-        System.out.println("Enter Array elements: ");
+        System.out.println("Enter Array elements in non-decreasing (sorted) order: ");
         int arr[] = new int[size];
         for (int i = 0; i < size; i++) {
             arr[i] = sc.nextInt();
         }
         System.out.println("Entered Array: " + Arrays.toString(arr));
+
+        if (!isSorted(arr)) {
+            System.out.println("Invalid input: Uniform Binary Search requires a sorted array in non-decreasing order.");
+            sc.close();
+            return;
+        }
+
         System.out.println("Enter the key element to be Found: ");
         int key = sc.nextInt();
         int result = binunisearch(arr, key);
@@ -20,6 +27,7 @@ public static void main(String[] args) {
         } else {
             System.out.println("Element " + key + " was NOT Found in the entered Array.");
         }
+        sc.close();
     }
     public static int binunisearch(int[] arr, int key) {
         int n = arr.length;
@@ -42,4 +50,13 @@ public static int binunisearch(int[] arr, int key) {
             return index;
         return -1;
     }
+
+    public static boolean isSorted(int[] arr) {
+        for (int i = 1; i < arr.length; i++) {
+            if (arr[i] < arr[i - 1]) {
+                return false;
+            }
+        }
+        return true;
+    }
 }