COS126

• Download Repeat.java

/*************************************************************************
 * Name:
 * NetID:
 * Precept:
 *
 * Description: Four methods, each of which produce a string of N
 * consecutive x's. (e.g., x, xx, xxx, xxxx)
 *************************************************************************/

public class Repeat {

    // returns a String of N consecutive x's
    public static String repeat1(int N) {
        char[] temp = new char[N];
        for (int i = 0; i < N; i++)
            temp[i] = 'x';
        return new String(temp);
    }
    
    // returns a String of N consecutive x's
    public static String repeat2(int N) {
        if      (N == 0) return "";
        else if (N == 1) return "x";
        else return repeat2(N / 2) + repeat2(N - (N / 2));
    }

    
    // returns a String of N consecutive x's
    public static String repeat3(int N) {
        if      (N == 0) return "";
        String temp = repeat3(N / 2);
        if (N % 2 == 0) return temp + temp;
        else            return temp + temp + "x";
    }

    // returns a String of N consecutive x's
    public static String repeat4(int N) {
        String s = "";
        for (int i = 0; i < N; i++)
            s = s + "x";
        return s;
    }

    public static void main(String[] args) { 
        int N = Integer.parseInt(args[0]);

        double start, end;
        String s;

        // run experiment 1 - invoke repeat1
        start = System.currentTimeMillis() / 1000.0;
        s = repeat1(N);
        end = System.currentTimeMillis() / 1000.0;
        StdOut.println("Elapsed time for repeat1() = " + (end - start));

        // run experiment 2 - invoke repeat2
        start = System.currentTimeMillis() / 1000.0;
        s = repeat2(N);
        end = System.currentTimeMillis() / 1000.0;
        StdOut.println("Elapsed time for repeat2() = " + (end - start));

        // run experiment 3 - invoke repeat3
        start = System.currentTimeMillis() / 1000.0;
        s = repeat3(N);
        end = System.currentTimeMillis() / 1000.0;
        StdOut.println("Elapsed time for repeat3() = " + (end - start));

        // run experiment 4 - invoke repeat4
        start = System.currentTimeMillis() / 1000.0;
        s = repeat4(N);
        end = System.currentTimeMillis() / 1000.0;
        StdOut.println("Elapsed time for repeat4() = " + (end - start));
    }
}