Binary search intro for Ayush & Pallavi

BinSearch.java

package practice.search;

/**
 * Created by ysharma on 9/18/16.
 */
public class BinSearch {

    public static boolean doIt(int[] arr, int elem){
        // return type is boolean .. since we dont have index of elements anyways. we are working on values.
        int start = arr[0];
        int end = arr[arr.length - 1];

        while(start <= end){
            int midValue = (start + end) / 2; // is a value //
            System.out.println("start:" + start + ",end:" + end);

            if(midValue == elem){
                return true;
            } else if (midValue > elem){ // elem is smaller than mid, so look in the part before mid..
                // Search before
                end = midValue - 1;
            } else {
                // search after
                start = midValue + 1;
            }
        }

        return false;
    }


    public static int doItOnIndex(int[] arr, int elem){
        int start = 0;
        int end = arr.length - 1;

        while(start <= end){
            int midValue = (start + end) / 2; // is a index //
            System.out.println("start:" + start + ",end:" + end);

            if(arr[midValue] == elem){
                return midValue;
            } else if (arr[midValue] > elem){ // elem is smaller than mid, so look in the part before mid..
                // Search before
                end = midValue - 1;
            } else {
                // search after
                start = midValue + 1;
            }
        }

        return -1;
    }


    public static int diItRecursive(int[] arr, int elem, int start, int end){
        int mid = (start + end) /2;
        System.out.println("start:" + start + ",end:" + end);

        if(arr[mid] == elem){
            return mid;
        } else if (arr[mid] > elem){ // elem is smaller than mid, so look in the part before mid..
            // Search before
            return diItRecursive(arr, elem, start, mid - 1);
        } else {
            // search after
            return diItRecursive(arr, elem, mid + 1, end);
        }
    }


    public static void main(String[] args) {
        int[] arr = {1,2,3,4,5,6,7,8,9,10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20000000};
        System.out.println(doIt(arr, 8));
        System.out.println(doItOnIndex(arr, 8));
        System.out.println(diItRecursive(arr, 8, 0, arr.length-1));
    }
}