Programming Praxis

6 Responses to “License Plates”

1. Rutger said

   May 16, 2017 at 11:07 AM

   In Python

   from collections import defaultdict
   
   class license_plates:
           # assumes plates of format ABC-123
   	def __init__(self):
   		self.collection = defaultdict(lambda : defaultdict(lambda : defaultdict(list)))
   
   	def __str__(self):
   		result = "List of plates in license_plate collection:"
   		for l1 in self.collection:
   			for l2 in self.collection[l1]:
   				for l3 in self.collection[l1][l2]:
   					for n in self.collection[l1][l2][l3]:
   						result+= "\n"+ l1+l2+l3+"-"+n
   		return result
   
   
   	def add_plate(self, plate):
   		if len(plate) != 7 and all(plate[i] in string.letters for i in range(3)):
   			raise
   		else:
   			self.collection[plate[0]][plate[1]][plate[2]].append(plate[4:7])
   
   
   	def print_plates_starting_with(self, start_letters):
   		if start_letters and len(start_letters) < 4:
   			d = self.collection
   			for l in start_letters:
   				d = d[l]
   			print("Plates starting with:", start_letters)
   			self.pretty_print_dict(start_letters, d)
   		else:
   			raise
   
   
   	def pretty_print_dict(self, prefix, d):
   		for key in d:
   			# print('\t' * indent + str(key))
   			if isinstance(d[key], dict):
   				self.pretty_print_dict(prefix+key, d[key])
   			else:
   				for n in d[key]:
   					print(prefix + key + '-' + n)
   
   
   lp = license_plates()
   lp.add_plate('ABC-123')
   lp.add_plate('ABH-666')
   lp.add_plate('AQC-987')
   lp.add_plate('DEF-000')
   
   print(lp)
   
   lp.print_plates_starting_with('A')
   lp.print_plates_starting_with('AB')
   lp.print_plates_starting_with('D')
   lp.print_plates_starting_with('X')
   
   # output:
   # List of plates in license_plate collection:
   # DEF-000
   # AQC-987
   # ABH-666
   # ABC-123
   # Plates starting with: A
   # AQC-987
   # ABH-666
   # ABC-123
   # Plates starting with: AB
   # ABH-666
   # ABC-123
   # Plates starting with: D
   # DEF-000
   # Plates starting with: X
   # [Finished in 0.2s]
   
   
2. Steve said

   May 16, 2017 at 8:53 PM

   MUMPS V1

   
   LICPLATE  ;New routine
            N CT,I,PLATES
            ; Add plates to array
            ;
            F I="PLB-123","PLB-666","PLB-987","PLC-000" D
            . S PLATES(I)=""
            ; Is PLB-123 member of the array?
            W !,"PLB is ",$S($D(PLATES("PLB-123")):"",1:"not"),"a member of the array."
            ;
            ; How many license plates begin with 'PLB'?
            ;
            S I=$O(PLATES("PLB"),-1) ; Start immediately before entries starting with 'PLB'
            F CT=0:1 S I=$O(PLATES(I)) Q:I'?1"PLB".E
            W !!,CT," plate",$S(CT'=1:"s",1:"")," begin with 'PLB'."
            ;
            ; What is the list of license plates that begin with the 'PLB'
            ;
            W !!,"List of license plates that begin with 'PLB':"
            S I=$O(PLATES("PLB"),-1) ; Start immediately before entries starting with 'PLB'
            F  S I=$O(PLATES(I)) Q:I'?1"PLB".E  W !,I
            Q
   
   ---
   
   D ^LICPLATE
   
   PLB is a member of the array.
   
   3 plates begin with 'PLB'.
   
   List of license plates that begin with 'PLB':
   PLB-123
   PLB-666
   PLB-987
   
   
3. bookofstevegraham said

   May 16, 2017 at 8:56 PM

   MUMPS V1

   
   Correction
   
   LICPLATE  ;New routine
            N CT,I,PLATES
            ; Add plates to array
            ;
            F I="PLB-123","PLB-666","PLB-987","PLC-000" D
            . S PLATES(I)=""
            ; Is PLB-123 member of the array?
            W !,"PLB-123 is ",$S($D(PLATES("PLB-123")):"",1:"not"),"a member of the array."
            ;
            ; How many license plates begin with 'PLB'?
            ;
            S I=$O(PLATES("PLB"),-1) ; Start immediately before entries starting with 'PLB'
            F CT=0:1 S I=$O(PLATES(I)) Q:I'?1"PLB".E
            W !!,CT," plate",$S(CT'=1:"s",1:"")," begin with 'PLB'."
            ;
            ; What is the list of license plates that begin with the 'PLB'
            ;
            W !!,"List of license plates that begin with 'PLB':"
            S I=$O(PLATES("PLB"),-1) ; Start immediately before entries starting with 'PLB'
            F  S I=$O(PLATES(I)) Q:I'?1"PLB".E  W !,I
            Q
   
   ---
   
   D ^LICPLATE
   
   PLB is a member of the array.
   
   3 plates begin with 'PLB'.
   
   List of license plates that begin with 'PLB':
   PLB-123
   PLB-666
   PLB-987
   
   
4. Paul said

   May 18, 2017 at 1:58 PM

   Using SQLite.

   import sqlite3 as db
   import random
   import string
   
   def create_random_plates():
       'fill the database with some license plates'
       with db.connect("license2.db") as DB:
           cur = DB.cursor()
           cur.execute('CREATE TABLE LicensePlates(Id INT, Chr TEXT)')
           for i in range(100000):
               c = "".join(random.sample(string.ascii_uppercase, 3))
               n = "".join(random.sample(string.digits, 3))
               cur.execute("""INSERT INTO LicensePlates Values({},
                           "{}-{}")""".format(i+1, c, n))
   
   def find_pattern(pattern):
       'pattern for SQL LIKE'
       with db.connect("license2.db") as DB:
           cur = DB.cursor()
           cur.execute("""SELECT * FROM LicensePlates
                       WHERE Chr LIKE '{}'
                       ORDER BY Chr""".format(pattern))
           return cur.fetchall()
   
   create_random_plates()
   #  find all plates starting with PLB and with 5 in middle of number
   for plate in find_pattern("PLB-_5_"):
       print(plate[1])
   
   """
   PLB-451
   PLB-652
   PLB-756
   PLB-956
   """
   
5. john said

   June 7, 2017 at 11:04 PM

   I used this shell program to generate a list of license plate numbers:

   
#!/bin/bash

   NUM_TIMES=100000
for ((i == 0 ; i < NUM_TIMES ; i++)); do
HEAD=$(head -c 3 < /dev/urandom | tr --complement 'A-Z' 'A-ZA-ZA-ZA-ZA-ZA-ZA-ZA-Z')
TAIL=$(head -c 3 < /dev/urandom | tr --complement '0-9' '0-90-90-90-90-90-90-90-90-90-90-90-90-90-90-90-90-90-90-90-90-90-90-90-9')
echo $HEAD-$TAIL
done


   Then I piped it through sort and uniq to make a list with no duplicates into cleaned.txt.

   Then I can use this shell program to query in the 3 ways required (membership, prefix count, and prefix listing):

   
#!/bin/bash

   case "$1" in
(member) # membership query #
<cleaned.txt grep --silent '^'"$2"'$'
if test "$?" -eq 0
then
echo "'$2' is a member of this set."
else
echo "'$2' is not a member of this set."
exit 1
fi
;;
(prefix) # prefix count #
COUNT=$(<cleaned.txt grep --count '^'"$2")
if test "$COUNT" -eq 0
then
echo "No license plates begin with '$2'."
exit 1
elif test "$COUNT" -eq 1
then
echo "1 license plate begins with '$2'."
else
echo "$COUNT license plates begin with '$2'."
fi
;;
(list) # prefix list #
<cleaned.txt grep '^'"$2"
if test "$?" -ne 0
then
echo "No license plates begin with '$2'."
exit 1
fi
;;
(*)
echo "unknown command - use 'member', 'prefix', or 'list'."
exit 1
;;
esac

6. john said

   June 7, 2017 at 11:07 PM

   edit of above comment:

   
#!/bin/bash

   NUM_TIMES=100000
for ((i == 0 ; i < NUM_TIMES ; i++)); do
    HEAD=$(head -c 3 < /dev/urandom | tr --complement 'A-Z' 'A-ZA-ZA-ZA-ZA-ZA-ZA-ZA-Z')
    TAIL=$(head -c 3 < /dev/urandom | tr --complement '0-9' '0-90-90-90-90-90-90-90-90-90-90-90-90-90-90-90-90-90-90-90-90-90-90-90-9')
    echo $HEAD-$TAIL
done


   —

   
#!/bin/bash

   case "$1" in
    (member) # membership query #
        <cleaned.txt grep --silent '^'"$2"'$'
        if test "$?" -eq 0
        then
            echo "'$2' is a member of this set."
        else
            echo "'$2' is not a member of this set."
            exit 1
        fi
        ;;
    (prefix) # prefix count #
        COUNT=$(<cleaned.txt grep --count '^'"$2")
        if test "$COUNT" -eq 0
        then
            echo "No license plates begin with '$2'."
            exit 1
        elif test "$COUNT" -eq 1
        then
            echo "1 license plate begins with '$2'."
        else
            echo "$COUNT license plates begin with '$2'."
        fi
        ;;
    (list) # prefix list #
        <cleaned.txt grep '^'"$2"
        if test "$?" -ne 0
        then
            echo "No license plates begin with '$2'."
            exit 1
        fi
        ;;
    (*)
        >&2 echo "unknown command - use 'member', 'prefix', or 'list'."
        exit 1
        ;;
esac