// Exercise 2.3.1 (Solution published at http://algs4.cs.princeton.edu/)
package algs23;
import stdlib.*;
import java.awt.Font;
/* ***********************************************************************
 *  Compilation:  javac TracePartition.java
 *  Execution:    java TracePartition string
 *
 *  Partitions the array of characters specified as the command-line
 *  argument and shows the detailed trace.
 *
 *  % java TracePartition KRATELEPUIMQCXOS
 *
 *  % java TracePartition AAAAAAAAAAAAAAAA
 *
 *************************************************************************/

public class XTracePartition {
  private static int line = 0;

  private static int partition(String[] a) {
    int lo = 0, hi = a.length - 1;
    int i = lo;
    int j = hi + 1;
    String v = a[lo];
    while (true) {

      // find item on lo to swap
      int iold = i + 1;
      while (less(a[++i], v))
        if (i == hi) break;

      // find item on hi to swap
      int jold = j - 1;
      while (less(v, a[--j]))
        if (j == lo) break;      // redundant since a[lo] acts as sentinel

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

      draw(a, iold, i, jold, j);
      line++;

      exch(a, i, j);
      draw(a, i, j);
      line++;
    }

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

    // 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);
  }

  private static void draw(String[] a, int iold, int ith, int jold, int jth) {
    StdDraw.setPenColor(StdDraw.BLACK);
    StdDraw.text(-2.50, line, ith  + "");
    StdDraw.text(-1.25, line, jth  + "");
    for (int i = 0; i < a.length; i++) {
      if      (i >= iold && i <= ith) StdDraw.setPenColor(StdDraw.BLACK);
      else if (i <= jold && i >= jth) StdDraw.setPenColor(StdDraw.BLACK);
      else                            StdDraw.setPenColor(StdDraw.LIGHT_GRAY);
      StdDraw.text(i, line, a[i]);
    }
  }

  private static void draw(String[] a, int ith, int jth) {
    StdDraw.setPenColor(StdDraw.BOOK_RED);
    StdDraw.text(-2.50, line, ith  + "");
    StdDraw.text(-1.25, line, jth  + "");
    for (int i = 0; i < a.length; i++) {
      if      (i == ith || i == jth) StdDraw.setPenColor(StdDraw.BOOK_RED);
      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, -3, "a[ ]");
    for (int i = 0; i < N; i++)
      StdDraw.text(i, -2, i + "");
    StdDraw.text(-2.50, -2, "i");
    StdDraw.text(-1.25, -2, "j");
    StdDraw.setPenColor(StdDraw.BOOK_RED);
    StdDraw.line(-3, -1.65, N-.5, -1.65);
    StdDraw.setPenColor(StdDraw.BLACK);
    for (int i = 0; i < a.length; i++)
      StdDraw.text(i, -1, a[i]);
  }

  // display footer
  private static void footer(String[] a, int j) {
    int N = a.length;
    StdDraw.setPenColor(StdDraw.BOOK_RED);
    StdDraw.text(-1.25, line, j + "");
    for (int i = 0; i < N; i++) {
      if  (i == j) StdDraw.setPenColor(StdDraw.BOOK_RED);
      else         StdDraw.setPenColor(StdDraw.BLACK);
      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
    int j = partition(a);

    // display the footer
    footer(a, j);
  }

}