BinarySearch.java

import java.io.*;
import java.util.*;

public class BinarySearch {

    static int binarySearch(int[] a, int x) {
        int left = 0, right = a.length - 1;

        while (left <= right) {
            int middle = left + (right - left) / 2;

            // checking if the middle element is equal to x
            if (a[middle] == x)
                return middle;

            // if x is greater than the middle element, then we can ignore the
            // left half of the array
            if (a[middle] < x)
                left = middle + 1;

            // if x is less than the middle element, then we can ignore the
            // right half respectively
            else
                right = middle - 1;
        }

        // if we have not found an index
        return -1;
    }

    static int linearSearch(int[] a, int x) {
        for (int i = 0; i < a.length; i++) {
            if (a[i] == x)
                return i;
        }

        return -1;
    }

    public static void main(String[] args) {
        FastScanner scanner = new FastScanner(System.in);
        int n = scanner.nextInt();
        int[] a = new int[n];

        for (int i = 0; i < n; i++) {
            a[i] = scanner.nextInt();
        }

        int m = scanner.nextInt();
        int[] b = new int[m];

        for (int i = 0; i < m; i++) {
            b[i] = scanner.nextInt();
        }

        for (int i = 0; i < m; i++) {
            System.out.print(binarySearch(a, b[i]) + " ");
        }
    }

    static class FastScanner {
        BufferedReader br;
        StringTokenizer st;

        FastScanner(InputStream stream) {
            try {
                br = new BufferedReader(new InputStreamReader(stream));
            } catch (Exception e) {
                e.printStackTrace();
            }
        }

        String next() {
            while (st == null || !st.hasMoreTokens()) {
                try {
                    st = new StringTokenizer(br.readLine());
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            return st.nextToken();
        }

        int nextInt() {
            return Integer.parseInt(next());
        }
    }
}