// Exercise 2.3.2 (Solution published at http://algs4.cs.princeton.edu/)
package algs23;
import stdlib.*;
import java.awt.Font;
/* ***********************************************************************
 *  Compilation:  javac TraceQuick.java
 *  Execution:    java  TraceQuick input
 *
 *  Quicksort the sequence of strings specified as the command-line
 *  arguments and show the detailed trace.
 *
 *  % java TraceQuick QUICKSORTEXAMPLE
 *
 *************************************************************************/

public class XTraceQuick {
  private static int line = 0;


  public static void sort(String[] a) {
    sort(a, 0, a.length - 1);
  }

  private static void sort(String[] a, int lo, int hi) {
    if (hi < lo) return;
    if (hi == lo) {
      draw(a, lo);
      line++;
      return;
    }
    int j = partition(a, lo, hi);
    draw(a, lo, j, hi);
    line++;
    sort(a, lo, j-1);
    sort(a, j+1, hi);
  }

  private static int partition(String[] a, int lo, int hi) {
    int i = lo;
    int j = hi + 1;
    String v = a[lo];
    while (true) {

      // find item on lo to swap
      while (less(a[++i], v))
        if (i == hi) break;

      // find item on hi to swap
      while (less(v, a[--j]))
        if (j == lo) break;      // redundant since a[lo] acts as sentinel

      // check if pointers cross
      if (i >= j) break;

      exch(a, i, j);
    }

    // put v = a[j] into position
    exch(a, lo, j);

    // with a[lo .. j-1] <= a[j] <= a[j+1 .. hi]
    return j;
  }


  // exchange a[i] and a[j]
  private static void exch(String[] a, int i, int j) {
    String swap = a[i];
    a[i] = a[j];
    a[j] = swap;
  }

  // is v < w ?
  private static boolean less(String v, String w) {
    return (v.compareTo(w) < 0);
  }

  // draw the contents of the array, with a[lo] in red
  private static void draw(String[] a, int lo) {
    StdDraw.setPenColor(StdDraw.LIGHT_GRAY);
    StdDraw.text(-3.75, line, lo + "");
    StdDraw.text(-1.25, line, lo + "");
    for (int i = 0; i < a.length; i++) {
      if (i == lo)  StdDraw.setPenColor(StdDraw.BOOK_RED);
      else          StdDraw.setPenColor(StdDraw.LIGHT_GRAY);
      StdDraw.text(i, line, a[i]);
    }
  }


  // draw the contents of the array, with a[lo] to a[hi] in black
  private static void draw(String[] a, int lo, int j, int hi) {
    StdDraw.setPenColor(StdDraw.BLACK);
    StdDraw.text(-3.75, line, lo + "");
    StdDraw.text(-1.25, line, hi + "");
    StdDraw.setPenColor(StdDraw.BOOK_RED);
    StdDraw.text(-2.50, line, j  + "");
    for (int i = 0; i < a.length; i++) {
      if (i == j)                  StdDraw.setPenColor(StdDraw.BOOK_RED);
      else if (i >= lo && i <= hi) StdDraw.setPenColor(StdDraw.BLACK);
      else                         StdDraw.setPenColor(StdDraw.LIGHT_GRAY);
      StdDraw.text(i, line, a[i]);
    }
  }

  // display header
  private static void header(String[] a) {
    int N = a.length;
    StdDraw.setPenColor(StdDraw.BLACK);
    StdDraw.text(N/2.0, -4, "a[ ]");
    for (int i = 0; i < N; i++)
      StdDraw.text(i, -3, i + "");
    StdDraw.text(-3.75, -3, "lo");
    StdDraw.text(-2.50, -3, "j");
    StdDraw.text(-1.25, -3, "hi");
    StdDraw.setPenColor(StdDraw.BOOK_RED);
    StdDraw.line(-4, -2.65, N-.5, -2.65);
    StdDraw.setPenColor(StdDraw.BLACK);
    for (int i = 0; i < a.length; i++)
      StdDraw.text(i, -2, a[i]);
    StdRandom.shuffle(a);
    for (int i = 0; i < a.length; i++)
      StdDraw.text(i, -1, a[i]);
  }

  // display footer
  private static void footer(String[] a) {
    int N = a.length;
    StdDraw.setPenColor(StdDraw.BLACK);
    for (int i = 0; i < N; i++)
      StdDraw.text(i, line, a[i]);
  }


  // test client
  public static void main(String[] args) {
    args = new String[] { "SORTEXAMPLE" };

    // parse command-line argument as an array of 1-character strings
    String s = args[0];
    int N = s.length();
    String[] a = new String[N];
    for (int i = 0; i < N; i++)
      a[i] = s.substring(i, i+1);

    // set canvas size
    StdDraw.setCanvasSize(30*(N+3), 30*(N+3));
    StdDraw.setXscale(-4, N+1);
    StdDraw.setYscale(N+1, -4);
    StdDraw.setFont(new Font("SansSerif", Font.PLAIN, 13));

    // display the header
    header(a);

    // sort the array and display trace
    sort(a);

    // display the footer
    footer(a);
  }

}