binary_search.java

/**
 * Created by xynophon on 15.1.13.
 */
public class binary_search {
    public int binary_search(double[] arr, double target){
        int lo = 0;
        int hi = arr.length;

        while(lo+1 < hi){
            int mid = (lo+hi)/2;
            if(target < arr[mid]){
                hi = mid;
            }else{
                lo = mid;
            }
        }
        if(arr[lo] == target) {
            return lo;
        }else{
            return -1;
        }
    }

    public int binary_search_rec(double[]arr, int lo, int hi, int target){
        int mid = (lo+hi)/2;
        if(lo+1 < hi) {
            if (arr[mid] == target) {
                return mid;
            } else {
                if (arr[mid] > target) {
                    hi = mid;
                } else {
                    lo = mid;
                }
            }
        }else{
            return -1;
        }
        return binary_search_rec(arr, lo, hi, target);
    }

    public static void main(String args[]){
        binary_search bs = new binary_search();
        double[] arr = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10};
        System.out.println("binary search index : " + bs.binary_search(arr, 11));
        System.out.println("binary search index : " + bs.binary_search_rec(arr, 0, arr.length, 6));
    }
}