package algs51;

import java.util.Arrays;
import java.util.Random;
import java.util.function.Consumer;
import stdlib.*;

/*
 * Using random.nextInt ():
 * RESULTS WITH Arrays.sort (Quicksort - Bentley/McIlroy 3-way)
 *
 *  2560000 [0.383 1.544]
 *  5120000 [0.672 1.755]
 * 10240000 [1.238 1.842]
 *
 * RESULTS WITH LSD
 *
 *  2560000 [0.064 0.889]
 *  5120000 [0.127 1.984]
 * 10240000 [0.195 1.535]
 */

public class XLSDInt {
  private static int byteAt(int i, int d) {
    return (i>>>(d*8)) & 0xff;
  }
  public static void sort(int[] a, boolean show) {
    int W = 4;
    int N = a.length;
    int R = 256;   // one byte
    int[] b = new int[N];
    for (int d = 0; d <= W-1; d++) {
      int[] count = new int[R+1];
      for (int i = 0; i < N; i++)
        count[byteAt(a[i], d) + 1]++;
      for (int r = 0; r < R; r++)
        count[r+1] += count[r];
      for (int i = 0; i < N; i++)
        b[count[byteAt(a[i], d)]++] = a[i];

      // copy back -- assumes that W is even!
      { int[] tmp = b; b = a; a = tmp; }
      if (show) show(a);
    }
  }
  private static boolean isSorted(int[] a) {
    for (int i = a.length-1; i > 0; i--)
      if (a[i] < a[i-1]) return false;
    return true;
  }
  private static void show(int[] a) {
    int W = 4;
    for (int i = 0; i < a.length; i++) {
      for (int d = W-1; d >= 0; d--)
        StdOut.format ("%02x ", byteAt(a[i], d));
      StdOut.println ();
    }
    StdOut.println ();
  }



  /* *********************************************************************************
   *  Test code
   ***********************************************************************************/
  private static void exch(int[] a, int i, int j) {
    int swap = a[i];
    a[i] = a[j];
    a[j] = swap;
  }
  private static double time;
  private static void countops (int N, Consumer<int[]> sort) {
    Random random = new Random();
    int[] a = new int[N];
    for (int i = 0; i < a.length; i++) a[i] = random.nextInt () & 0x7fffffff; // positive numbers

    Stopwatch sw = new Stopwatch ();
    sort.accept (a);
    time = sw.elapsedTime ();
    if (!isSorted(a)) throw new Error();
  }
  public static void run(String name, Consumer<int[]> sort) {
    StdOut.println (name);
    int N = 1280000;
    countops (N, sort);
    double prevTime = time;
    for (int i=0; i<3; i++) {
      N *= 2;
      countops (N, sort);
      StdOut.format("%8d [%5.3f %5.3f]\n", N, time, time/prevTime);
      prevTime = time;
    }
  }

  public static void main(String[] args) {
    run ("LSD", (a) -> sort (a, false));
    run ("Quicksort", (a) -> Arrays.sort (a));
  }
  public static void main1(String[] args) {
    Random random = new Random();
    int[] a = new int[10];
    for (int i = 0; i < a.length; i++) a[i] = random.nextInt () & 0x7fffffff; // positive numbers
    show (a);
    sort (a, true);
  }
}