Lennot

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

import sys
from sys import stdin
from sys import stdout

maxint = sys.maxint

def readline():
    return stdin.readline().strip()

line1 = readline().split(' ')
# Kaupunkeja
n = int(line1[0])
# Lentoja
m = int(line1[1])

class Flight:
    def __init__(self, a, b, h):
        self.fr = a
        self.to = b
        self.price = int(h)

class City:
    def __init__(self, aid):
        self.total_price = maxint
        self.even = True
        self.calculated = False
        self.con_fr = []
        self.con_to = []
        self.aid = aid
        self.remove = False
    def __eq__(self, other):
        return (isinstance(other, self.__class__)
            and self.aid == other.aid)


flights = []
cities = []
for c in xrange(n):
    cities.append(City(c))

uncalculated = list(cities)

for f in xrange(m):
    row = readline().split(' ')
    flight = Flight(cities[int(row[0])-1], cities[int(row[1])-1], row[2])
    flights.append(flight)
    flight.fr.con_to.append(flight)
    flight.to.con_fr.append(flight)


start = cities[0]
end = cities[-1]
start.total_price = 0



for repeat in xrange(n*20-1):
    for city in cities:
        if city.total_price != maxint:
            for flight in city.con_to:
                city_to = flight.to
                if city.even:
                    new_value = city.total_price + flight.price
                else:
                    new_value = city.total_price
                if new_value < city_to.total_price:
                    city_to.total_price = new_value
                    city_to.even = not city.even

print(end.total_price)
    # for flight in current.con_to:
    #     city = flight.to
    #     if not city.calculated:
    #         if current.even_price_set:
    #             new_odd_price = current.total_price_even + flight.price
    #             if new_odd_price < city.total_price_odd:
    #                 city.total_price_odd = new_odd_price
    #                 city.odd_price_set = True
    #
    #         if current.odd_price_set:
    #             new_even_price = current.total_price_odd
    #             if new_even_price < city.total_price_even:
    #                 city.total_price_even = new_even_price
    #                 city.even_price_set = True
    # uncalculated.remove(current)
    # current.calculated = True
    # if current == end:
    #     found = True
    #     print(min(current.total_price_even, current.total_price_odd))
    #     # if current.total_price_even < maxint and current.total_price_odd < maxint:
    #     #     raise
    #     break
    #
    # smallest_price = maxint
    # for city in reversed(uncalculated):
    #     # cityprice = city.total_price_even + city.total_price_odd
    #     cityprice = min(city.total_price_even, city.total_price_odd)
    #     if cityprice < smallest_price:
    #         smallest = city
    #         smallest_price = cityprice
    #
    # current = smallest

Test 1

Group: 1

Verdict: WRONG ANSWER

Test 2

Group: 1

Verdict: ACCEPTED

Test 3

Group: 1

Verdict: ACCEPTED

Test 4

Group: 1

Verdict: ACCEPTED

Test 5

Group: 1

Verdict: ACCEPTED

Test 6

Group: 2

Verdict: TIME LIMIT EXCEEDED

Test 7

Group: 2

Verdict: TIME LIMIT EXCEEDED

Test 8

Group: 2

Verdict: TIME LIMIT EXCEEDED

Test 9

Group: 2

Verdict: TIME LIMIT EXCEEDED

Test 10

Group: 2

Verdict: TIME LIMIT EXCEEDED

Test 11

Group: 3

Verdict: RUNTIME ERROR

Test 12

Group: 3

Verdict: RUNTIME ERROR

Test 13

Group: 3

Verdict: RUNTIME ERROR

Test 14

Group: 3

Verdict: RUNTIME ERROR

Test 15

Group: 3

Verdict: RUNTIME ERROR

Test 16

Group: 3

Verdict: RUNTIME ERROR

Test 17

Group: 3

Verdict: RUNTIME ERROR