"""File:     srch_tst2.py
   Purpose:  Compare the run-time of binary search, linear search,
             and dictionary search on a list of ints

   Run:      python srch_tst2.py

   Input:    The number of ints in the data structure.  The number of 
             values to search for.
   Output:   The average time it took to search the list using
             binary and linear search and a dictionary.
"""
from random import randint
from time import time

#----------------------------------------------------------------------
def dict_srch(d, key):
   """Search the dictionary d for key"""
   if d.has_key(key):
      return d[key]
   else:
      return None

#----------------------------------------------------------------------
def bin_srch(l, min, max, key):
   """See if key belongs to l between subscript min and subscript max"""
   if (min <= max):
      mid = (min+max)/2
      if key == l[mid]:
         return mid
      elif key < l[mid]:
         return bin_srch(l, min, mid-1, key)
      else: # key > l[mid]
         return bin_srch(l, mid+1, max, key)
   else: # min > max.  key not in list
      return None

#----------------------------------------------------------------------
def lin_srch(l, key):
   """Use linear search to try to find key in l"""
   for i in xrange(len(l)):
      if l[i] == key:
         return i
   return None

#----------------------------------------------------------------------
def gen_list(n, max):
   """Generate a list of n random ints in the range 0--max"""
   l = []
   for i in xrange(n):
      l.append(randint(0,max))
   return l


#----------------------------------------------------------------------
def gen_dict(l):
   """Create a dictionary from the list l"""
   d = dict()
   count = 0
   for i in l:
      d[i] = count
      count = count+1
   return d

#----------------------------------------------------------------------
# Main program
n = int(raw_input("How many elements in the list?\n   "))
srch_count = int(raw_input("How many elements should we search for?\n   "))

l = gen_list(n, 2*n)
l.sort()
d = gen_dict(l)
#print "l =", l
#print "d =", d

srch_keys = gen_list(srch_count, 2*n)
#print "srch_keys =", srch_keys

start = time()
for i in xrange(srch_count):
   loc = bin_srch(l, 0, n-1, srch_keys[i])
#  print "bin_srch: ", srch_keys[i], "in loc", loc
finish = time()
bin_srch_time = finish-start;
print "Average time for bin search =", bin_srch_time/srch_count

start = time()
for i in xrange(srch_count):
   loc = lin_srch(l, srch_keys[i])
#  print "lin_srch: ", srch_keys[i], "in loc", loc
finish = time()
lin_srch_time = finish-start;
print "Average time for lin search =", lin_srch_time/srch_count

start = time()
for i in xrange(srch_count):
   loc = dict_srch(d, srch_keys[i])
#  print "dict_srch: ", srch_keys[i], "in loc", loc
finish = time()
dict_srch_time = finish-start;
print "Average time to dict search for =", dict_srch_time/srch_count