#! /usr/bin/env python

"""csed problem posed by Owen Astrachan, Duke Univ.
Solution in Python by Bob Noonan, College of William and Mary

Algorithm:
a.   break words on whitespace
b.  use hashtable to maintain count of each word
c.  for each word in hashtable, put it in a 2D array,
    where first dimension is frequency of word
d.  sort each sublist starting from high end,
    and then print each sorted sublist
"""

import string, sys, os

max = 0

def printf(format, *args):
    """printf from Python Cookbook, 2nd ed, p 183"""
    sys.stdout.write(format % args)

def readFile(fn):
    """reads file fn into a hash list"""
    global max
    inn = open(fn, "rU");
    list = { }
    for line in inn:
	words = string.split(line)
	for w in words:
	    w = w.lower() + " "
	    if not list.has_key(w): list[w] = 0
	    list[w]= list[w]+1
	    if list[w] > max: max = list[w]
    # print "max = ", max
    return list

def printlist(ct, words):
    """print a sorted list of words with same frequenct"""
    for w in words:
	printf("%d\t%s\n", ct, w.rstrip())

def sortlist(list, words):
    """ctreate a 2D word list where the row index"""
    """ is the frequency count"""
    for w in list.keys():
	val = list[w]
	# print "val = ", val
	words[val].append(w)
    for i in range(max, 0, -1):
	words[i].sort()
	printlist(i, words[i])


def main():
    """main function"""
    global max
    list = readFile(sys.argv[1])
    words = [ ]
    for i in range(0, max+1):
	w = [ ]
	words.append(w)
    # print "len = ", len(words)
    sortlist(list, words)
    # for w in list.keys():
	# print w, "\t", list[w]

main()