Lennot

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

import sys
from sys import stdin
from sys import stdout
# import profile # debug

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_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
        self.remove = False


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


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

    # Purge all unnecessary cities
    removes = []
    for city_i in xrange(1, n-1):
        city = cities[city_i]
        if len(city.con_to) == 0:
            removes.append(city)

    for city in removes:
        cities.remove(city)

    start = cities[0]
    end = cities[-1]
    current = start
    
    uncalculated = [current]

    current.total_price_even = 0
    current.even_price_set = True
    
    
    def select_next():
        if len(uncalculated) != 0:
            smallest_price = maxint
            for city in reversed(uncalculated):
                # cityprice = city.total_price_even + city.total_price_odd
                cityprice = city.total_price
                if cityprice < smallest_price:
                    smallest = city
                    smallest_price = cityprice
            
            return smallest
    
    found = False
    while not found:
        
        for flight in current.con_to:
            city = flight.to
            price_changed = False
            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
                    price_changed = 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
                    price_changed = True
            if price_changed:
                price = city.total_price = min(city.total_price_even, city.total_price_odd)
                if city.calculated:
                    city.calculated = False
                    uncalculated.append(city)
                    city.in_uncalc = True
                if not city.in_uncalc:
                    uncalculated.append(city)
                    city.in_uncalc = True
        
        uncalculated.remove(current)
        current.calculated = True
        
        if current.aid == end.aid:
            found = True
            print(end.total_price)
            break
        
        current = select_next()
# 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: 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