C ++
Longitud total: 9059, Área total: 27469, Fallas: 13.
Nota: El puntaje incluye penalizaciones por falla.
Salida de muestra:
a 6 b 8 c 11 d 11 e 11 f 11 g 12 h 15 i 18 j 18 k 21 l 23 m 26 n 28 o 28 p 30 q 32 r 33 s 33 t 34
------ae
| |
|---c
b||-g
|d|
f |
i---|
k---| h
| j
|---m
l | t
o-n|
|s-r
|-|
p q
Length: 39, Area: 150.
a 6 b 6 c 6 d 6 e 6 f 6 g 6 h 8 i 9 j 9 k 9 l 12 m 12 n 13 o 14 p 15 q 15 r 15 s 17 t 17 u 17 v 17 w 17 x 20 y 23 z 26
------a n|--w
|d-||---k|-o|
| g|b |--m --x
|-|c ||--r|
||f l|-q |
||--j u--|--s|-
e|-i |p| y|
h v t z-
Length: 56, Area: 120.
Salida completa: http://pastebin.com/raw.php?i=spBUidBV
¿No te encantan las soluciones de fuerza bruta? Esto es un poco más que un simple algoritmo de retroceso: nuestro trabajador incansable se mueve por el mapa, colocando fusibles y fuegos artificiales según sea necesario, mientras prueba todos los movimientos posibles en cualquier momento. Bueno, casi --- restringimos el conjunto de movimientos y abandonamos los estados no óptimos de manera temprana para que no tome un tiempo insoportable (y, en particular, para que termine). Se tiene especial cuidado de no crear ningún ciclo o no intencional caminos y no volver por donde vinimos, así que está garantizado que no visitemos el mismo estado dos veces. Aun así, encontrar una solución óptima puede llevar un tiempo, por lo que eventualmente renunciamos a optimizar una solución si lleva demasiado tiempo.
Este algoritmo todavía tiene algo de margen. Por un lado, se pueden encontrar mejores soluciones aumentando los FRUSTRATIONparámetros. No hay cajeros automáticos de la competencia, pero estos números se pueden aumentar si y cuando ...
Compilar con: g++ fireworks.cpp -ofireworks -std=c++11 -pthread -O3.
Ejecutar con: ./fireworks.
Lee la entrada de STDIN y escribe la salida en STDOUT (posiblemente fuera de servicio).
/* Magic numbers */
#define THREAD_COUNT 2
/* When FRUSTRATION_MOVES moves have passed since the last solution was found,
* the last (1-FRUSTRATION_STATES_BACKOFF)*100% of the backtracking states are
* discarded and FRUSTRATION_MOVES is multiplied by FRUSTRATION_MOVES_BACKOFF.
* The lower these values are, the faster the algorithm is going to give up on
* searching for better solutions. */
#define FRUSTRATION_MOVES 1000000
#define FRUSTRATION_MOVES_BACKOFF 0.8
#define FRUSTRATION_STATES_BACKOFF 0.5
#include <iostream>
#include <vector>
#include <algorithm>
#include <utility>
#include <thread>
#include <mutex>
#include <string>
#include <sstream>
#include <cassert>
using namespace std;
/* A tile on the board. Either a fuse, a firework, an empty tile or an
* out-of-boudns tile. */
struct tile {
/* The tile's value, encoded the "obvious" way (i.e. '-', '|', 'a', etc.)
* Empty tiles are encoded as '\0' and OOB tiles as '*'. */
char value;
/* For fuse tiles, the time at which the fuse is lit. */
int time;
operator char&() { return value; }
operator const char&() const { return value; }
bool is_fuse() const { return value == '-' || value == '|'; }
/* A tile is vacant if it's empty or OOB. */
bool is_vacant() const { return !value || value == '*'; }
/* Prints the tile. */
template <typename C, typename T>
friend basic_ostream<C, T>& operator<<(basic_ostream<C, T>& os,
const tile& t) {
return os << (t.value ? t.value : ' ');
}
};
/* Fireworks have the same encoding as tiles. */
typedef tile firework;
typedef vector<firework> fireworks;
/* The fuse map. It has physical dimensions (its bounding-box) but is
* conceptually infinite (filled with empty tiles.) */
class board {
/* The tiles, ordered left-to-right top-to-bottom. */
vector<tile> p_data;
/* The board dimensions. */
int p_width, p_height;
/* The total fuse length. */
int p_length;
public:
board(): p_width(0), p_height(0), p_length(0) {}
/* Physical dimensions. */
int width() const { return p_width; }
int height() const { return p_height; }
int area() const { return width() * height(); }
/* Total fuse length. */
int length() const { return p_length; }
/* Returns the tile at (x, y). If x or y are negative, returns an OOB
* tile. */
tile get(int x, int y) const {
if (x < 0 || y < 0)
return {'*'};
else if (x >= width() || y >= height())
return {'\0'};
else
return p_data[y * width() + x];
}
/* Sets the tile at (x, y). x and y must be nonnegative and the tile at
* (x, y) must be empty. */
board& set(int x, int y, const tile& t) & {
assert(x >= 0 && y >= 0);
assert(!get(x, y));
if (x >= width() || y >= height()) {
int new_width = x >= width() ? x + 1 : width();
int new_height = y >= height() ? y + 1 : height();
vector<tile> temp(new_width * new_height, {'\0'});
for (int l = 0; l < height(); ++l)
copy(
p_data.begin() + l * width(),
p_data.begin() + (l + 1) * width(),
temp.begin() + l * new_width
);
p_data.swap(temp);
p_width = new_width;
p_height = new_height;
}
p_data[y * width() + x] = t;
if (t.is_fuse())
++p_length;
return *this;
}
board&& set(int x, int y, const tile& t) && { return move(set(x, y, t)); }
/* Prints the board. */
template <typename C, typename T>
friend basic_ostream<C, T>& operator<<(basic_ostream<C, T>& os,
const board& b) {
for (int y = 0; y < b.height(); ++y) {
for (int x = 0; x < b.width(); ++x)
os << b.get(x, y);
os << endl;
}
return os;
}
};
/* A state of the tiling algorithm. */
struct state {
/* The current board. */
board b;
/* The next firework to tile. */
fireworks::const_iterator fw;
/* The current location. */
int x, y;
/* The current movement direction. 'N'orth 'S'outh 'E'ast, 'W'est or
* 'A'ny. */
char dir;
};
/* Adds a state to the state-stack if its total fuse length and bounding-box
* area are not worse than the current best ones. */
void add_state(vector<state>& states, int max_length, int max_area,
state&& new_s) {
if (new_s.b.length() < max_length ||
(new_s.b.length() == max_length && new_s.b.area() <= max_area)
)
states.push_back(move(new_s));
}
/* Adds the state after moving in a given direction, if it's a valid move. */
void add_movement(vector<state>& states, int max_length, int max_area,
const state& s, char dir) {
int x = s.x, y = s.y;
char parallel_fuse;
switch (dir) {
case 'E': if (s.dir == 'W') return; ++x; parallel_fuse = '|'; break;
case 'W': if (s.dir == 'E') return; --x; parallel_fuse = '|'; break;
case 'S': if (s.dir == 'N') return; ++y; parallel_fuse = '-'; break;
case 'N': if (s.dir == 'S') return; --y; parallel_fuse = '-'; break;
}
const tile t = s.b.get(s.x, s.y), nt = s.b.get(x, y);
assert(t.is_fuse());
if (nt.is_fuse() && !(t == parallel_fuse && nt == parallel_fuse))
add_state(states, max_length, max_area, {s.b, s.fw, x, y, dir});
}
/* Adds the state after moving in a given direction and tiling a fuse, if it's a
* valid move. */
void add_fuse(vector<state>& states, int max_length, int max_area,
const state& s, char dir, char fuse) {
int x = s.x, y = s.y;
int sgn;
bool horz;
switch (dir) {
case 'E': ++x; sgn = 1; horz = true; break;
case 'W': --x; sgn = -1; horz = true; break;
case 'S': ++y; sgn = 1; horz = false; break;
case 'N': --y; sgn = -1; horz = false; break;
}
if (s.b.get(x, y))
/* Tile is not empty. */
return;
/* Make sure we don't create cycles or reconnect a firework. */
const tile t = s.b.get(s.x, s.y);
assert(t.is_fuse());
if (t == '-') {
if (horz) {
if (fuse == '-') {
if (!s.b.get(x + sgn, y).is_vacant() ||
s.b.get(x, y - 1) == '|' ||
s.b.get(x, y + 1) == '|')
return;
} else {
if (s.b.get(x + sgn, y) == '-' ||
!s.b.get(x, y - 1).is_vacant() ||
!s.b.get(x, y + 1).is_vacant())
return;
}
} else {
if (!s.b.get(x, y + sgn).is_vacant() ||
s.b.get(x - 1, y) == '-' ||
s.b.get(x + 1, y) == '-')
return;
}
} else {
if (!horz) {
if (fuse == '|') {
if (!s.b.get(x, y + sgn).is_vacant() ||
s.b.get(x - 1, y) == '-' ||
s.b.get(x + 1, y) == '-')
return;
} else {
if (s.b.get(x, y + sgn) == '|' ||
!s.b.get(x - 1, y).is_vacant() ||
!s.b.get(x + 1, y).is_vacant())
return;
}
} else {
if (!s.b.get(x + sgn, y).is_vacant() ||
s.b.get(x, y - 1) == '|' ||
s.b.get(x, y + 1) == '|')
return;
}
}
/* Ok. */
add_state(
states,
max_length,
max_area,
{board(s.b).set(x, y, {fuse, t.time + 1}), s.fw, x, y, dir}
);
}
/* Adds the state after adding a firework at the given direction, if it's a
* valid move. */
void add_firework(vector<state>& states, int max_length, int max_area,
const state& s, char dir) {
int x = s.x, y = s.y;
int sgn;
bool horz;
switch (dir) {
case 'E': ++x; sgn = 1; horz = true; break;
case 'W': --x; sgn = -1; horz = true; break;
case 'S': ++y; sgn = 1; horz = false; break;
case 'N': --y; sgn = -1; horz = false; break;
}
if (s.b.get(x, y))
/* Tile is not empty. */
return;
/* Make sure we don't run into an undeliberate fuse. */
if (horz) {
if (s.b.get(x + sgn, y) == '-' || s.b.get(x, y - 1) == '|' ||
s.b.get(x, y + 1) == '|')
return;
} else {
if (s.b.get(x, y + sgn) == '|' || s.b.get(x - 1, y) == '-' ||
s.b.get(x + 1, y) == '-')
return;
}
/* Ok. */
add_state(
states,
max_length,
max_area,
/* After adding a firework, we can move in any direction. */
{board(s.b).set(x, y, {*s.fw}), s.fw + 1, s.x, s.y, 'A'}
);
}
void add_possible_moves(vector<state>& states, int max_length, int max_area,
const state& s) {
/* We add the new states in reverse-desirability order. The most
* (aesthetically) desirable states are added last. */
const tile t = s.b.get(s.x, s.y);
assert(t.is_fuse());
/* Move in all (possible) directions. */
for (char dir : "WENS")
if (dir) add_movement(states, max_length, max_area, s, dir);
/* If the fuse is too short for the next firework, keep adding fuse. */
if (t.time < s.fw->time) {
if (t == '-') {
add_fuse(states, max_length, max_area, s, 'N', '|');
add_fuse(states, max_length, max_area, s, 'S', '|');
add_fuse(states, max_length, max_area, s, 'W', '|');
add_fuse(states, max_length, max_area, s, 'W', '-');
add_fuse(states, max_length, max_area, s, 'E', '|');
add_fuse(states, max_length, max_area, s, 'E', '-');
} else {
add_fuse(states, max_length, max_area, s, 'W', '-');
add_fuse(states, max_length, max_area, s, 'E', '-');
add_fuse(states, max_length, max_area, s, 'N', '-');
add_fuse(states, max_length, max_area, s, 'N', '|');
add_fuse(states, max_length, max_area, s, 'S', '-');
add_fuse(states, max_length, max_area, s, 'S', '|');
}
} else if (t.time == s.fw->time) {
/* If we have enough fuse for the next firework, place the firework (if
* possible) and don't add more fuse, or else we'll never finish... */
if (t == '-') {
add_firework(states, max_length, max_area, s, 'W');
add_firework(states, max_length, max_area, s, 'E');
} else {
add_firework(states, max_length, max_area, s, 'N');
add_firework(states, max_length, max_area, s, 'S');
}
}
}
void thread_proc(mutex& lock, int& total_length, int& total_area,
int& failures) {
fireworks fw;
vector<state> states;
while (true) {
/* Read input. */
string input;
{
lock_guard<mutex> lg(lock);
while (!cin.eof() && input.empty())
getline(cin, input);
if (input.empty())
break;
}
fw.clear();
int length = 0, area;
{
stringstream is;
is << input;
while (!is.eof()) {
char c;
int t;
if (is >> c >> t) {
/* Fireworks must be sorted by launch time. */
assert(fw.empty() || t >= fw.back().time);
fw.push_back({c, t});
length += t;
}
}
assert(!fw.empty());
area = fw.back().time * fw.back().time;
}
/* Add initial state. */
states.push_back({board().set(0, 0, {'-', 1}), fw.begin(), 0, 0, 'A'});
board solution;
int moves = 0;
int frustration_moves = FRUSTRATION_MOVES;
while (!states.empty()) {
/* Check for solutions (all fireworks consumed.) */
while (!states.empty() && states.back().fw == fw.end()) {
state& s = states.back();
/* Did we find a better solution? */
if (solution.area() == 0 || s.b.length() < length ||
(s.b.length() == length && s.b.area() < area)
) {
solution = move(s.b);
moves = 0;
length = solution.length();
area = solution.area();
}
states.pop_back();
}
/* Expand the top state. */
if (!states.empty()) {
state s = move(states.back());
states.pop_back();
add_possible_moves(states, length, area, s);
}
/* Getting frustrated? */
++moves;
if (moves > frustration_moves) {
/* Get rid of some data. */
states.erase(
states.begin() + states.size() * FRUSTRATION_STATES_BACKOFF,
states.end()
);
frustration_moves *= FRUSTRATION_MOVES_BACKOFF;
moves = 0;
}
}
/* Print solution. */
{
lock_guard<mutex> lg(lock);
cout << input << endl;
if (solution.area())
cout << solution;
else {
cout << "FAILED!" << endl;
++failures;
}
cout << "Length: " << length <<
", Area: " << area <<
"." << endl << endl;
total_length += length;
total_area += area;
}
}
}
int main(int argc, const char* argv[]) {
thread threads[THREAD_COUNT];
mutex lock;
int total_length = 0, total_area = 0, failures = 0;
for (int i = 0; i < THREAD_COUNT; ++i)
threads[i] = thread(thread_proc, ref(lock), ref(total_length),
ref(total_area), ref(failures));
for (int i = 0; i < THREAD_COUNT; ++i)
threads[i].join();
cout << "Total Length: " << total_length <<
", Total Area: " << total_area <<
", Failures: " << failures <<
"." << endl;
}
Pitón
Longitud total: 17387, Área total: 62285, Fallas: 44.
Salida de muestra:
a 6 b 8 c 11 d 11 e 11 f 11 g 12 h 15 i 18 j 18 k 21 l 23 m 26 n 28 o 28 p 30 q 32 r 33 s 33 t 34
------a
|----f
|---c
b|||---h
|dg |
e |-j
|---k
i |
|---m
l |-o
|--p
n |--s
|-r
q|
t
Length: 45, Area: 345.
Salida completa: http://pastebin.com/raw.php?i=mgiqXCRK
Como referencia, aquí hay un enfoque mucho más simple. Intenta conectar los fuegos artificiales a una sola línea de fusibles principales, creando una forma de "escalera". Si un fuego artificial no puede conectarse directamente a la línea principal (lo que ocurre cuando dos o más fuegos artificiales se encienden al mismo tiempo), rastrea la línea principal buscando un punto en el que pueda ramificarse perpendicularmente hacia abajo o hacia la derecha (y falla si no existe tal punto.)
Como era de esperar, lo hace peor que el solucionador de fuerza bruta, pero no por un gran margen. Honestamente, esperaba que la diferencia fuera algo mayor.
Ejecutar con: python fireworks.py.
from __future__ import print_function
import sys
total_length = total_area = failures = 0
for line in sys.stdin:
# Read input.
line = line.strip()
if line == "": continue
fws = line.split(' ')
# The fireworks are a list of pairs of the form (<letter>, <time>).
fws = [(fws[i], int(fws[i + 1])) for i in xrange(0, len(fws), 2)]
# The board is a dictionary of the form <coord>: <tile>.
# The first tile marks the "starting point" and is out-of-bounds.
board = {(-1, 0): '*'}
# The tip of the main "staircase" fuse.
tip_x, tip_y = -1, 0
tip_time = 0
# We didn't fail. Yet...
failed = False
for (fw, fw_time) in fws:
dt = fw_time - tip_time
# Can we add the firework to the main fuse line?
if dt > 0:
# We can. Alternate the direction to create a "staircase" pattern.
if board[(tip_x, tip_y)] == '-': dx, dy = 0, 1; fuse = '|'
else: dx, dy = 1, 0; fuse = '-'
x, y = tip_x, tip_y
tip_x += dt * dx
tip_y += dt * dy
tip_time += dt
else:
# We can't. Trace the main fuse back until we find a point where we
# can thread, or fail if we reach the starting point.
x, y = tip_x, tip_y
while board[(x, y)] != '*':
horz = board[(x, y)] == '-'
if horz: dx, dy = 0, 1; fuse = '|'
else: dx, dy = 1, 0; fuse = '-'
if dt > 0 and (x + dx, y + dy) not in board: break
if horz: x -= 1
else: y -= 1
dt += 1
if board[(x, y)] == '*':
failed = True
break
# Add the fuse and firework.
for i in xrange(dt):
x += dx; y += dy
board[(x, y)] = fuse
board[(x + dx, y + dy)] = fw
# Print output.
print(line)
if not failed:
max_x, max_y = (max(board, key=lambda p: p[i])[i] + 1 for i in (0, 1))
for y in xrange(max_y):
for x in xrange(max_x):
print(board.get((x, y), ' '), end = "")
print()
length = len(board) - len(fws) - 1
area = max_x * max_y
else:
print("FAILED!")
failures += 1
length = sum(map(lambda fw: fw[1], fws))
area = fws[-1][1] ** 2
print("Length: %d, Area: %d.\n" % (length, area))
total_length += length; total_area += area
print("Total Length: %d, Total Area: %d, Failures: %d." %
(total_length, total_area, failures))