package edu.princeton.cs.excercise.ch2;
/*************************************************************************
* 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
*
*************************************************************************/
import edu.princeton.cs.introcs.StdDraw;
import edu.princeton.cs.introcs.StdRandom;
import java.awt.Font;
public class TraceQuick {
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) {
StdDraw.setPenColor(StdDraw.BLACK);
for (int i = 0; i < a.length; i++)
StdDraw.text(i, line, a[i]);
}
// test client
public static void main(String[] args) {
// 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);
}
}