CodeIQ の「迷路」問題の僕の回答

#!/usr/bin/env python
# -*- coding: utf-8 -*-
import sqlite3


def main():
    try:
        conn = sqlite3.connect(':memory:')
        # conn = sqlite3.connect('testDB')
        strSQL = '''
CREATE TABLE node(
    node TEXT CONSTRAINT pk_node PRIMARY KEY
    , dist integer);
--WITH N(n) AS (
--        SELECT UNICODE('0')
--        UNION ALL SELECT n + 1 FROM N WHERE n < UNICODE('9'))
--    INSERT INTO node(node) SELECT char(n) FROM N;
--WITH N(n) as (
--        SELECT UNICODE('A')
--        UNION ALL SELECT n + 1 FROM N WHERE n < UNICODE('Z'))
--    INSERT INTO node(node) SELECT char(n) FROM N;
CREATE TABLE edge(
    node1 TEXT
    , node2 TEXT
    , CONSTRAINT pk_edge PRIMARY KEY(
        node1
        , node2));
INSERT INTO edge
    VALUES
        ('0','6')
        , ('1','2')
        , ('2','3')
        , ('2','8')
        , ('3','4')
        , ('4','5')
        , ('4','A')
        , ('6','7')
        , ('7','8')
        , ('9','A')
        , ('9','F')
        , ('A','G')
        , ('B','H')
        , ('C','D')
        , ('D','J')
        , ('E','K')
        , ('H','N')
        , ('I','J')
        , ('I','O')
        , ('J','K')
        , ('J','P')
        , ('K','L')
        , ('M','N')
        , ('M','S')
        , ('N','T')
        , ('O','U')
        , ('Q','R')
        , ('Q','W')
        , ('R','S')
        , ('T','Z')
        , ('U','V')
        , ('V','W')
        , ('X','Y')
        , ('Y','Z')
        ;
INSERT INTO edge(node1, node2)
    SELECT
            node2, node1
        FROM
            edge
        --WHERE
        --    node1 < node2
        ;
'''
        conn.executescript(strSQL)
        strInput = input()
        opengate = strInput[0]
        strStart = strInput[1]
        strend = strInput[2]
        strSQL = '''
INSERT INTO edge VALUES (:node1,:node2),(:node2,:node1)
'''
        if opengate == 'a':
            conn.execute(strSQL, {'node1': '7', 'node2': 'D'})
        elif opengate == 'b':
            conn.execute(strSQL, {'node1': 'E', 'node2': 'F'})
        elif opengate == 'c':
            conn.execute(strSQL, {'node1': 'G', 'node2': 'M'})
        elif opengate == 'd':
            conn.execute(strSQL, {'node1': 'A', 'node2': 'B'})
        strSQL = '''
INSERT INTO node VALUES(?, 0);
'''
        conn.execute(strSQL, (strStart,))
        strSQL_AddNode = '''
INSERT INTO node
    SELECT
        node2, nS.dist + 1
    FROM
        edge
        INNER JOIN node nS
        ON edge.node1 = nS.node
        LEFT OUTER JOIN node nE
        ON edge.node2 = nE.node
    WHERE
        nE.node is null;
'''
        strSQL_GetDistance = '''
    SELECT
            dist
        FROM
            node
        WHERE
            node.node = ?
'''
        cur = conn.cursor()
        while(True):
            conn.execute(strSQL_AddNode)
            rows = cur.execute(strSQL_GetDistance, (strend,)).fetchall()
            if len(rows) > 0:
                break
        print(rows[0][0])
    finally:
        # conn.commit()
        conn.close()


if __name__ == '__main__':
    main()