BinarySearch.java

package algorithms.search.binary;

/**
 * Searches for a target value in a sorted array using binary search.
 * <p>
 * Time Complexity: O(log n) in all cases.
 * Space Complexity: O(1).
 * <p>
 * Use when: Searching in sorted arrays repeatedly.
 * Avoid when: Array is unsorted (use linear search) or only one search (linear may be simpler).
 * Requirement: Array MUST be sorted.
 */
class BinarySearch {

    static int binarySearch(int[] arr, int target) {
        int low = 0;
        int high = arr.length;

        while (low < high) {
            int mid = (low + high) / 2;

            if (arr[mid] == target)
                return mid;

            if (arr[mid] < target)
                low = mid;
            else
                high = mid;
        }

        return -1;
    }

    public static void main(String[] args) {
        int[] sortedArray = new int[]{4, 8, 15, 16, 23, 42};

        System.out.println(binarySearch(sortedArray, 3));
        System.out.println(binarySearch(sortedArray, 23));
        System.out.println(binarySearch(sortedArray, 8));
    }
}