Binary & Linear Search Java

SearchingAlgorithms/Java/BinarySearch.java

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+// Sudarshan Hiray
+// 4th October 2020
+// Given an Array of Integers and element to be searched, following program will search the element through Binary search.
+// Elements MUST be sorted for binary search.
+// Binary search uses Divide And Conquer technique.
+// In each step, the algorithm compares the input element x with the value of the middle element in array. 
+// If the values match, return the index of the middle. Otherwise, if x is less than the middle element, 
+// then the algorithm recurs for left side of middle element, else recurs for the right side of the middle element.
+
+import java.util.Scanner;
+
+public class BinarySearch
+{
+    public static void main(String[] args){
+        Scanner scanner = new Scanner(System.in);
+
+        System.out.println("Please enter size of the array");
+        int size = scanner.nextInt();
+        System.out.println("Please enter "+size+ " elements of the array");
+        System.out.println("Enter elements in Ascending order as Binary search can work only with Sorted elements");
+        int[] intArray = new int[size];
+        for(int i=0;i<size;i++){
+            intArray[i] = scanner.nextInt();
+            if(i>0 && intArray[i]<intArray[i-1]){
+                System.out.println("Element entered was not in ascending order.. Exiting, please re-run and enter elements in Ascending order");
+                System.exit(0);
+            }
+        }
+
+        System.out.println("Please enter element to be searched in the array");
+        int elementToFind = scanner.nextInt();
+
+        int position = binarySearch(intArray, 0, size, elementToFind);
+        if(position != -1)
+            System.out.println("Element "+ elementToFind +" is FOUND at position "+ (position+1) + " in the given array");
+        else
+            System.out.println("Element "+ elementToFind +" is NOT FOUND in the given array");
+    }
+
+    public static int binarySearch(int A[], int left, int right,  int k){
+        if(left > right)
+            return -1;
+        int mid = (left + right)/2;
+        if(A[mid] == k)
+            return mid;
+        else if(A[mid] < k)
+            return binarySearch(A, mid+1, right, k);
+        else if(A[mid] > k)
+            return binarySearch(A, left, mid-1, k);
+        else
+            return -1;
+    }
+}

SearchingAlgorithms/Java/LinearSearch.java

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+// Sudarshan Hiray
+// 4th October 2020
+// Given an Array of Integers and element to be searched, following program will search the element through Linear search.
+// Linear search will go through all elements linearly even if element is at the end of the array. Hence its complexity is O(n).
+
+
+import java.util.Scanner;
+
+public class LinearSearch
+{
+    public static void main(String[] args){
+        Scanner scanner = new Scanner(System.in);
+
+        System.out.println("Please enter size of the array");
+        int size = scanner.nextInt();
+        System.out.println("Please enter "+size+ " elements of the array");
+        int[] intArray = new int[size];
+        for(int i=0;i<size;i++){
+            intArray[i] = scanner.nextInt();
+        }
+
+        System.out.println("Please enter element to be searched in the array");
+        int elementToFind = scanner.nextInt();
+
+        int position = linearSearch(intArray, elementToFind);
+        if(position != -1)
+            System.out.println("Element "+ elementToFind +" is FOUND at position "+ (position+1) + " in the given array");
+        else
+            System.out.println("Element "+ elementToFind +" is NOT FOUND in the given array");
+    }
+
+    public static int linearSearch(int[] array, int elementToFind){
+        for(int i=0;i<array.length;i++){
+            if(array[i] == elementToFind)
+                return i;
+        }
+        return -1;
+    }
+}