package edu.princeton.cs.excercise.ch2;
/*************************************************************************
* Compilation: javac TraceMergeBU.java
* Execution: java TraceMergeBU input
*
* Mergesort the sequence of strings specified as the command-line
* arguments and show the detailed trace.
*
* % java TraceMergeBU MERGESORTEXAMPLE
*
*************************************************************************/
import edu.princeton.cs.introcs.StdDraw;
import java.awt.Font;
public class TraceMergeBU {
private static void merge(String[] a, String[] aux, int lo, int m, int hi) {
// copy to aux[]
for (int k = lo; k <= hi; k++) {
aux[k] = a[k];
}
// merge back to a[]
int i = lo, j = m+1;
for (int k = lo; k <= hi; k++) {
if (i > m) a[k] = aux[j++];
else if (j > hi) a[k] = aux[i++];
else if (less(aux[j], aux[i])) a[k] = aux[j++];
else a[k] = aux[i++];
}
}
// bottom-up mergesort
public static void sort(String[] a) {
int line = 0;
int N = a.length;
String[] aux = new String[N];
for (int n = 1; n < N; n = n+n) {
for (int i = 0; i < N-n; i += n+n) {
int lo = i;
int m = i + n - 1;
int hi = Math.min(i + n + n - 1, N - 1);
merge(a, aux, lo, m, hi);
draw(a, line, lo, m, hi);
line++;
}
}
}
// 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] to a[hi] in black
private static void draw(String[] a, int line, int lo, int m, int hi) {
StdDraw.setPenColor(StdDraw.BLACK);
StdDraw.text(-2.50, line, m + "");
StdDraw.setPenColor(StdDraw.BOOK_RED);
StdDraw.text(-3.75, line, lo + "");
StdDraw.text(-1.25, line, hi + "");
for (int i = 0; i < a.length; i++) {
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, -3, "a[ ]");
for (int i = 0; i < N; i++)
StdDraw.text(i, -2, i + "");
StdDraw.text(-3.75, -2, "lo");
StdDraw.text(-2.50, -2, "m");
StdDraw.text(-1.25, -2, "hi");
StdDraw.setPenColor(StdDraw.BOOK_RED);
StdDraw.line(-4, -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 N = a.length;
StdDraw.setPenColor(StdDraw.BLACK);
for (int i = 0; i < a.length; i++)
StdDraw.text(i, N - 1, 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);
}
}