Write a program to perform binary search on a list of integers given below to search for an element input by the user. If it is found, display the element along with its position; otherwise, display the message "Search element not found."
5, 7, 9, 11, 15, 20, 30, 45, 89, 97

Java Programming Language (Article) (Program)

75

Given Input: 

5, 7, 9, 11, 15, 20, 30, 45, 89, 97

Expected Output: 

15 found at position 5

Program:

class BSearch {
    int A[] = {5, 7, 9, 11, 15, 20, 30, 45, 89, 97}; // Array of integers
    int low, high, mid, flag = 0; // Variables for binary search and flag for checking if element is found

    void display(int n) {
        low = 0; // Initialize low to the first index
        high = A.length - 1; // Initialize high to the last index
        
        while (low <= high) {
            mid = (low + high) / 2; // Calculate mid index
            
            if (n == A[mid]) { // If the element is found
                flag = 1;
                break;
            } else if (n > A[mid]) { // If the search element is greater, ignore the left half
                low = mid + 1;
            } else { // If the search element is smaller, ignore the right half
                high = mid - 1;
            }
        }
        
        if (flag == 1) {
            System.out.println(n + " found at position " + (mid + 1)); // Element found
        } else {
            System.out.println("Search element not found"); // Element not found
        }
    }
    
    public static void main(String args[]) {
        BSearch obj = new BSearch();
        obj.display(15); // Test the binary search with the element 15
    }
}

Output:

15 found at position 5

Explanation:

  1. Array Initialization:

    • int A[] = {5, 7, 9, 11, 15, 20, 30, 45, 89, 97}; defines the array of integers to be searched.

  2. Binary Search Logic:

    • The low, high, and mid variables help in narrowing down the search range.
    • The search continues by comparing the middle element (A[mid]) with the target (n). Depending on whether n is greater or lesser, the search range is adjusted by modifying low or high.

  3. Flag for Element Found:

    • flag = 1; indicates that the element has been found, which breaks the loop.

  4. Output:

    • If the element is found, the program prints its position (1-based index).
    • If not found, it prints "Search element not found".

Key Points:

  • This program searches for the integer 15 in the array, but you can modify obj.display(15); to search for any other integer.
  • The position is based on a 1-based index (i.e., starting from 1).

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