# MergeWorstCase.java

Below is the syntax highlighted version of MergeWorstCase.java from §2.2 Mergesort.

```/******************************************************************************
*  Compilation:  javac MergeWorstCase.java
*  Execution:    java MergeWorstCase n
*  Dependencies: StdOut.java StdIn.java
*
*  Create a worst-case input for mergesort that makes the maximum
*  number of compares possible.
*
*  % java MergeWorstCase 8
*  [0, 2, 1, 6, 4, 5, 3, 7]
*
*  % java MergeWorstCase 16
*  [0, 2, 1, 6, 4, 5, 3, 14, 8, 10, 9, 13, 11, 12, 7, 15]
*
*  % java MergeWorstCase 32
*  [0, 2, 1, 6, 4, 5, 3, 14, 8, 10, 9, 13, 11, 12, 7, 30, 16, 18, 17, 22, 20, 21, 19, 29, 24, 26, 25, 28, 23, 27, 15, 31]
*
******************************************************************************/

import java.util.Arrays;

public class MergeWorstCase {

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

// precondition a[lo..hi] contains distinct integers, with largest at a[hi]
private static void worst(int[] a, int lo, int hi) {
if (hi <= lo) return;
int mid = lo + (hi - lo) / 2;

// put second largest integer at a[mid]
int max = lo;
for (int i = lo + 1; i < hi; i++) {
if (a[i] > a[max]) max = i;
}
exch(a, max, mid);
worst(a, lo, mid);
worst(a, mid+1, hi);
}

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

public static void main(String[] args) {
int n = Integer.parseInt(args[0]);
int[] a = new int[n];
for (int i = 0; i < n; i++)
a[i] = i;
worst(a);
StdOut.println(Arrays.toString(a));
}
}
```