content: /*************************************************************************
   *  Compilation:  javac MergeBU.java
   *  Execution:    java MergeBU < input.txt
   *  Dependencies: StdOut.java StdIn.java
   *  Data files:   http://algs4.cs.princeton.edu/22merge/tiny.txt
   *                http://algs4.cs.princeton.edu/22merge/words3.txt
   *   
   *  Sorts a sequence of strings from standard input using
   *  bottom-up mergesort.
   *   
   *  % more tiny.txt
   *  S O R T E X A M P L E
   *
   *  % java MergeBU < tiny.txt
   *  S O R T E X A M P L E A               [ one string per line ]
   *    
   *  % more words3.txt
   *  bed bug dad yes zoo ... all bad yet
   *  
   *  % java MergeBU < words3.txt
   *  all bad bed bug dad ... yes yet zoo    [ one string per line ]
   *
   *************************************************************************/
  
  public class MergeBU {
  
  
  
      // stably merge a[lo..m] with a[m+1..hi] using aux[lo..hi]
      private static void merge(Comparable[] a, Comparable[] 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(Comparable[] a) {
          int N = a.length;
          Comparable[] aux = new Comparable[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);
              }
          }
          assert isSorted(a);
      }
  
    /***********************************************************************
      *  Helper sorting functions
      ***********************************************************************/
      
      // is v < w ?
      private static boolean less(Comparable v, Comparable w) {
          return (v.compareTo(w) < 0);
      }
  
     // exchange a[i] and a[j]
      private static void exch(Object[] a, int i, int j) {
          Object swap = a[i];
          a[i] = a[j];
          a[j] = swap;
      }
  
  
     /***********************************************************************
      *  Check if array is sorted - useful for debugging
      ***********************************************************************/
      private static boolean isSorted(Comparable[] a) {
          for (int i = 1; i < a.length; i++)
              if (less(a[i], a[i-1])) return false;
          return true;
      }
  
      // print array to standard output
      private static void show(Comparable[] a) {
          for (int i = 0; i < a.length; i++) {
              StdOut.println(a[i]);
          }
      }
  
      // Read strings from standard input, sort them, and print.
      public static void main(String[] args) {
          String[] a = StdIn.readStrings();
          MergeBU.sort(a);
          show(a);
      }
  }
  
  
  