Lennot

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

import sys
from sys import stdin
from sys import stdout
import gc

maxint = sys.maxint

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

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

# Tuple indexes
fl_from = 0
fl_to = 1
fl_price = 2

ct_total_price_even = 0
ct_even_price_set = 1
ct_total_price_odd = 2
ct_odd_price_set = 3
ct_total_price = 4
ct_calculated = 5
ct_con_to = 6
ct_in_uncalc = 7
ct_aid = 8



# def init_city(aid):
#     return list(city_template)

# class City:
#     def __init__(self, aid):
#         self.total_price_even = maxint
#         self.even_price_set = False
#         self.total_price_odd = maxint
#         self.odd_price_set = False
#         self.total_price = maxint
#         self.calculated = False
#         self.con_to = []
#         self.in_uncalc = False
#         self.aid = aid

# def purge(cities):
#     removes = []
#     for i, city in cities:
#         if i >= 1 and i < n-1:
#             if len(city[ct_con_to]) == 0:
#                 removes.append(city)
#
#
#     for city in removes:
#         cities.remove(city)
    


def run():
    def gen(i):
        return [maxint, False, maxint, False, maxint, False, [], False, i]
    cities = map(gen, xrange(n))
    

    for f in xrange(m):
        row = readline().split(' ')
        flight = (int(row[0])-1, int(row[1])-1, int(row[2]))
        cities[flight[fl_from]][ct_con_to].append(flight)
    # Purge all unnecessary cities
    # purge(cities)

    start = cities[0]
    end = cities[-1]
    current = start
    
    gc.collect()
    
    uncalculated = [current]
    append_to_uncalculated = uncalculated.append
    remove_from_uncalculated = uncalculated.remove

    current[ct_total_price_even] = 0
    current[ct_even_price_set] = True
    
    found = False
    while not found:
        even_set = current[ct_even_price_set]
        even_cur = current[ct_total_price_even]
        odd_set = current[ct_odd_price_set]
        odd_cur = current[ct_total_price_odd]
        for flight in current[ct_con_to]:
            city = cities[flight[fl_to]]
            price_changed = False
            if even_set:
                new_odd_price = even_cur + flight[fl_price]
                if new_odd_price < city[ct_total_price_odd]:
                    city[ct_total_price_odd] = new_odd_price
                    city[ct_odd_price_set] = True
                    price_changed = True
            
            if odd_set:
                new_even_price = odd_cur
                if new_even_price < city[ct_total_price_even]:
                    city[ct_total_price_even] = new_even_price
                    city[ct_even_price_set] = True
                    price_changed = True
            if price_changed:
                city[ct_total_price] = min(city[ct_total_price_even], city[ct_total_price_odd])
                if city[ct_calculated]:
                    city[ct_calculated] = False
                    append_to_uncalculated(city)
                    city[ct_in_uncalc] = True
                elif not city[ct_in_uncalc]:
                    append_to_uncalculated(city)
                    city[ct_in_uncalc] = True
        
        remove_from_uncalculated(current)
        current[ct_calculated] = True
        
        if current[ct_aid] == end[ct_aid]:
            found = True
            print(end[ct_total_price])
            break
        
        smallest_price = maxint
        for city in uncalculated:
            # cityprice = city.total_price_even + city.total_price_odd
            cityprice = city[ct_total_price]
            if cityprice < smallest_price:
                smallest = city
                smallest_price = cityprice
        
        current = smallest
        
# import profile # debug
# profile.run('run()')
run()

Test 1

Group: 1

Verdict: ACCEPTED

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: ACCEPTED

Test 7

Group: 2

Verdict: ACCEPTED

Test 8

Group: 2

Verdict: ACCEPTED

Test 9

Group: 2

Verdict: ACCEPTED

Test 10

Group: 2

Verdict: ACCEPTED

Test 11

Group: 3

Verdict: TIME LIMIT EXCEEDED

Test 12

Group: 3

Verdict: TIME LIMIT EXCEEDED

Test 13

Group: 3

Verdict: TIME LIMIT EXCEEDED

Test 14

Group: 3

Verdict: ACCEPTED

Test 15

Group: 3

Verdict: TIME LIMIT EXCEEDED

Test 16

Group: 3

Verdict: TIME LIMIT EXCEEDED

Test 17

Group: 3

Verdict: TIME LIMIT EXCEEDED