#include <set>
#include <algorithm>
+#define MIN_ROW 1
+#define MAX_ROW 75
+#define MIN_SWITCH 1
+#define MAX_SWITCH 6
+#define HEAP_MST 0
+#define USE_KOPT 1
+#define KOPT_SLICES 3
+#define KOPT_ITERATIONS 10000
+
+static const unsigned num_cache_elem = (MAX_ROW * MAX_SWITCH * 2) * (MAX_ROW * MAX_SWITCH * 2);
+static unsigned short dist_cache[(MAX_ROW * MAX_SWITCH * 2) * (MAX_ROW * MAX_SWITCH * 2)],
+ opt_dist_cache[MAX_ROW * MAX_SWITCH * MAX_ROW * MAX_SWITCH],
+ pess_dist_cache[MAX_ROW * MAX_SWITCH * MAX_ROW * MAX_SWITCH];
+
+inline unsigned short &cache(
+ unsigned row_from, unsigned switch_from, unsigned side_from,
+ unsigned row_to, unsigned switch_to, unsigned side_to)
+{
+ return dist_cache[(row_from * MAX_SWITCH * 2 + switch_from * 2 + side_from) * (MAX_ROW * MAX_SWITCH * 2) +
+ row_to * MAX_SWITCH * 2 + switch_to * 2 + side_to];
+}
+
+inline unsigned short &opt_cache(
+ unsigned row_from, unsigned switch_from,
+ unsigned row_to, unsigned switch_to)
+{
+ return opt_dist_cache[(row_from * MAX_SWITCH + switch_from) * (MAX_ROW * MAX_SWITCH) +
+ row_to * MAX_SWITCH + switch_to];
+}
+
+inline unsigned short &pess_cache(
+ unsigned row_from, unsigned switch_from,
+ unsigned row_to, unsigned switch_to)
+{
+ return pess_dist_cache[(row_from * MAX_SWITCH + switch_from) * (MAX_ROW * MAX_SWITCH) +
+ row_to * MAX_SWITCH + switch_to];
+}
+
struct order {
unsigned row, num;
int side;
int distance_row(unsigned from, unsigned to)
{
+ /* 4.1m per double row, plus gaps */
+ unsigned base_cost = 41 * abs(from - to);
+
+ if ((from <= 9) != (to <= 9))
+ base_cost += 25;
+ if ((from <= 17) != (to <= 17))
+ base_cost += 25;
+ if ((from <= 25) != (to <= 25))
+ base_cost += 25;
+ if ((from <= 34) != (to <= 34))
+ base_cost += 25;
+
/* don't calculate gaps here just yet, just estimate 4.1m per double row */
- return 41 * abs(from - to);
+ return base_cost;
}
-int distance(int row_from, int switch_from, int side_from, int row_to, int switch_to, int side_to)
+int pessimistic_distance(int row_from, int switch_from, int row_to, int switch_to)
{
- /* can we just walk directly? */
- if (row_from == row_to && side_from == side_to) {
- return distance_switch(switch_from, switch_to);
- }
-
- /* can we just switch sides? */
- if (row_from + 1 == row_to && side_from == 1 && side_to == 0) {
- return distance_switch(switch_from, switch_to);
- }
- if (row_from == row_to + 1 && side_from == 0 && side_to == 1) {
- return distance_switch(switch_from, switch_to);
- }
-
/* we'll need to go to one of the three middles */
int best2 = distance_middle(switch_from, 2) + distance_middle(switch_to, 2);
int distrow = distance_row(row_from, row_to);
}
}
+int distance(int row_from, int switch_from, int side_from, int row_to, int switch_to, int side_to)
+{
+ /* can we just walk directly? */
+ if (row_from == row_to && side_from == side_to) {
+ return distance_switch(switch_from, switch_to);
+ }
+
+ /* can we just switch sides? */
+ if (row_from + 1 == row_to && side_from == 1 && side_to == 0) {
+ return distance_switch(switch_from, switch_to) + distance_row(row_from, row_to) - 31;
+ }
+ if (row_from == row_to + 1 && side_from == 0 && side_to == 1) {
+ return distance_switch(switch_from, switch_to) + distance_row(row_from, row_to) - 31;
+ }
+
+ return pessimistic_distance(row_from, switch_from, row_to, switch_to);
+}
+
int optimistic_distance(int row_from, int switch_from, int row_to, int switch_to)
{
- if (abs(row_from - row_to) == 1)
+ if (row_from == row_to)
return distance_switch(switch_from, switch_to);
+ else if (abs(row_from - row_to) == 1)
+ return distance_switch(switch_from, switch_to) + distance_row(row_from, row_to) - 31;
else
- return distance(row_from, switch_from, 0, row_to, switch_to, 0);
+ return pessimistic_distance(row_from, switch_from, row_to, switch_to);
}
-// extremely primitive O(V^2) prim
+#if HEAP_MST
+// this is, surprisingly enough, _slower_ than the naive variant below, so it's not enabled
+struct prim_queue_val {
+ std::pair<unsigned, unsigned> dst;
+ int cost;
+
+ bool operator< (const prim_queue_val &other) const
+ {
+ return (cost > other.cost);
+ }
+};
+
+// standard O(V^2 log v) prim
+int prim_mst(std::set<std::pair<unsigned, unsigned> > &in)
+{
+ std::set<std::pair<unsigned, unsigned> > set2;
+ std::priority_queue<prim_queue_val> queue;
+
+ // pick the first one
+ std::set<std::pair<unsigned, unsigned> >::iterator start = in.begin();
+
+ unsigned row = start->first;
+ unsigned num = start->second;
+
+ set2.insert(*start);
+
+ // find all the edges out from it
+ for (std::set<std::pair<unsigned, unsigned> >::iterator j = in.begin(); j != in.end(); ++j) {
+ if (set2.count(*j))
+ continue;
+
+ unsigned d = opt_cache(row, num, j->first, j->second);
+ prim_queue_val val = { *j, d };
+ queue.push(val);
+ }
+
+ unsigned total_cost = 0;
+ while (set2.size() != in.size()) {
+invalid:
+ prim_queue_val val = queue.top();
+ queue.pop();
+
+ // check if dst is already moved
+ if (set2.count(val.dst))
+ goto invalid;
+
+ unsigned row = val.dst.first;
+ unsigned num = val.dst.second;
+ set2.insert(val.dst);
+
+ total_cost += val.cost;
+
+ // find all the edges from this new node
+ for (std::set<std::pair<unsigned, unsigned> >::iterator j = in.begin(); j != in.end(); ++j) {
+ if (set2.count(*j))
+ continue;
+
+ unsigned d = opt_cache(row, num, j->first, j->second);
+ prim_queue_val val = { *j, d };
+ queue.push(val);
+ }
+ }
+
+ return total_cost;
+}
+#else
+// extremely primitive O(V^3) prim
int prim_mst(std::set<std::pair<unsigned, unsigned> > &set1)
{
std::set<std::pair<unsigned, unsigned> > set2;
for (std::set<std::pair<unsigned, unsigned> >::iterator i = set1.begin(); i != set1.end(); ++i) {
for (std::set<std::pair<unsigned, unsigned> >::iterator j = set2.begin(); j != set2.end(); ++j) {
- unsigned d = optimistic_distance(i->first, i->second, j->first, j->second);
+ unsigned d = opt_cache(i->first, i->second, j->first, j->second);
if (d < best_this_cost) {
best_this_cost = d;
best_set1 = i;
return total_cost;
}
-
+#endif
void print_tour(std::vector<std::pair<unsigned, unsigned> > &points)
{
std::set<std::pair<unsigned, unsigned> > points_left;
+ unsigned total_cost = 0;
for (unsigned i = 0; i < points.size(); ++i) {
points_left.insert(points[i]);
}
for (unsigned i = 0; i < points.size(); ++i) {
+ printf("%2u: ", i);
if (best_tour[i].side == 0)
printf("%2u-%u (left side) ", best_tour[i].row, best_tour[i].num);
else
printf(" ");
} else {
printf("cost=%4u ", best_tour[i].cost);
+ total_cost += best_tour[i].cost;
}
// let's see how good the MST heuristics are
std::set<std::pair<unsigned, unsigned> >::iterator j = points_left.find(std::make_pair(best_tour[i].row, best_tour[i].num));
points_left.erase(j);
}
+ printf("Done (total_cost=%u)\n", total_cost);
+}
+
+bool any_opt;
+std::pair<unsigned, unsigned> best_reorganization[KOPT_SLICES];
+
+void optimize_specific_tour(order *tour, std::set<std::pair<unsigned, unsigned> > &fragments,
+ std::vector<std::pair<unsigned, unsigned> > &history, unsigned cost_so_far)
+{
+ if (fragments.size() == 1) {
+ if (cost_so_far < best_so_far) {
+ any_opt = true;
+ memcpy(best_reorganization, &history[0], sizeof(std::pair<unsigned, unsigned>)*history.size());
+ best_so_far = cost_so_far;
+ }
+ return;
+ }
+
+ // match the first point with all the others
+ std::set<std::pair<unsigned, unsigned> >::iterator start = fragments.begin();
+ std::pair<unsigned, unsigned> start_val = *start;
+
+ std::set<std::pair<unsigned, unsigned> >::iterator i = start;
+ ++i;
+
+ fragments.erase(start);
+
+ while (i != fragments.end()) {
+ std::pair<unsigned, unsigned> i_val = *i;
+ std::set<std::pair<unsigned, unsigned> >::iterator i_copy = i;
+ ++i;
+
+ unsigned p1 = start_val.second, p2 = i_val.first;
+ history[fragments.size() - 1] = std::make_pair(p1, p2);
+
+ unsigned this_cost = cache(
+ tour[p1].row, tour[p1].num, tour[p1].side,
+ tour[p2].row, tour[p2].num, tour[p2].side
+ );
+
+ std::set<std::pair<unsigned, unsigned> > frag_copy = fragments;
+ frag_copy.erase(frag_copy.find(i_val));
+ frag_copy.insert(std::make_pair(start_val.first, i_val.second));
+ optimize_specific_tour(tour, frag_copy, history, cost_so_far + this_cost);
+ }
+
+ fragments.insert(start_val);
+}
+
+void piece_fragment(std::vector<std::pair<unsigned, unsigned> > &points, order *ntour, std::set<std::pair<unsigned, unsigned> > &fragments, unsigned s, unsigned j)
+{
+ // find this fragment, and copy
+ for (std::set<std::pair<unsigned, unsigned> >::iterator i = fragments.begin(); i != fragments.end(); ++i) {
+ if (i->first != s)
+ continue;
+ memcpy(best_tour + j, ntour + s, sizeof(order) * (i->second - i->first + 1));
+
+ j += (i->second - i->first + 1);
+
+ // find the connection point, if any
+ for (unsigned k = 0; k < KOPT_SLICES; ++k) {
+ if (best_reorganization[k].first == i->second) {
+ piece_fragment(points, ntour, fragments, best_reorganization[k].second, j);
+ best_tour[j].cost =
+ cache(best_tour[j-1].row, best_tour[j-1].num, best_tour[j-1].side,
+ best_tour[j].row, best_tour[j].num, best_tour[j].side);
+ return;
+ }
+ }
+ }
+}
+
+void reorganize_tour(std::vector<std::pair<unsigned, unsigned> > &points, std::set<std::pair<unsigned, unsigned> > &fragments)
+{
+ order *ntour = new order[points.size()];
+ memcpy(ntour, best_tour, sizeof(order) * points.size());
+
+ piece_fragment(points, ntour, fragments, 0, 0);
+
+ delete[] ntour;
+}
+
+void optimize_tour(std::vector<std::pair<unsigned, unsigned> > &points)
+{
+ if (points.size() < KOPT_SLICES * 2) {
+ fprintf(stderr, "Warning: Too high KOPT_SLICES set (%u), can't optimize\n", KOPT_SLICES);
+ }
+
+ order *tour = new order[points.size()];
+ any_opt = false;
+
+ for (unsigned i = 0; i < KOPT_ITERATIONS; ++i) {
+ int cost = best_so_far;
+ memcpy(tour, best_tour, sizeof(order) * points.size());
+
+ for (unsigned j = 0; j < KOPT_SLICES; ++j) {
+ // we break the link between RR and RR+1.
+ unsigned rand_remove;
+ do {
+ rand_remove = (unsigned)((points.size() - 2) * (rand() / (RAND_MAX + 1.0)));
+ } while (tour[rand_remove + 1].cost == -1 || (rand_remove != 0 && tour[rand_remove].cost == -1));
+
+ cost -= tour[rand_remove + 1].cost;
+ tour[rand_remove + 1].cost = -1;
+ }
+
+ /* find the starts and the ends of each point */
+ int last_p = 0;
+ std::set<std::pair<unsigned, unsigned> > fragments;
+ for (unsigned j = 1; j < points.size(); ++j) {
+ if (tour[j].cost != -1)
+ continue;
+ fragments.insert(std::make_pair(last_p, j - 1));
+ last_p = j;
+ }
+ fragments.insert(std::make_pair(last_p, points.size() - 1));
+
+ /* brute force */
+ std::vector<std::pair<unsigned, unsigned> > history(KOPT_SLICES);
+ optimize_specific_tour(tour, fragments, history, cost);
+
+ if (any_opt) {
+ printf("\nk-opt reduced cost to %u:\n", best_so_far);
+
+ reorganize_tour(points, fragments);
+ print_tour(points);
+ optimize_tour(points);
+
+ return;
+ }
+ }
+
+ delete[] tour;
+
+ printf("\nk-opt made no further improvements.\n");
}
unsigned do_tsp(std::vector<std::pair<unsigned, unsigned> > &points, std::set<std::pair<unsigned, unsigned> > &points_left, order *ord, order *temp, unsigned ind, unsigned cost_so_far)
printf("\nNew best tour found! cost=%u\n", cost_so_far);
print_tour(points);
best_so_far = cost_so_far;
+#if USE_KOPT
+ optimize_tour(points);
+#endif
return 0;
}
+
+ unsigned last_row = ord[ind-1].row;
+ unsigned last_switch = ord[ind-1].num;
+ unsigned last_side = ord[ind-1].side;
+
+ /*
+ * The minimum spanning tree gives us a reliable lower bound for what we can
+ * achieve for the rest of the graph, so check it before doing anything else.
+ */
+ std::set<std::pair<unsigned, unsigned> > mst_set = points_left;
+ mst_set.insert(std::make_pair(last_row, last_switch));
+
+ unsigned min_rest_cost = prim_mst(mst_set);
+ if (cost_so_far + min_rest_cost >= best_so_far) {
+ return UINT_MAX;
+ }
/*
* Simple heuristic: always search for the closest points from this one first; that
* will give us a sizable cutoff.
*/
unsigned toi = 0;
- unsigned last_row = ord[ind-1].row;
- unsigned last_switch = ord[ind-1].num;
- unsigned last_side = ord[ind-1].side;
-
- std::set<std::pair<unsigned, unsigned> > mst_set = points_left;
- mst_set.insert(std::make_pair(last_row, last_switch));
for (std::set<std::pair<unsigned, unsigned> >::iterator i = points_left.begin(); i != points_left.end(); ++i) {
/* try both sides */
temp[toi].row = i->first;
temp[toi].num = i->second;
temp[toi].side = 0;
- temp[toi].cost = distance(last_row, last_switch, last_side, i->first, i->second, 0);
+ temp[toi].cost = cache(last_row, last_switch, last_side, i->first, i->second, 0);
++toi;
temp[toi].row = i->first;
temp[toi].num = i->second;
temp[toi].side = 1;
- temp[toi].cost = distance(last_row, last_switch, last_side, i->first, i->second, 1);
+ temp[toi].cost = cache(last_row, last_switch, last_side, i->first, i->second, 1);
++toi;
}
-
- unsigned min_rest_cost = prim_mst(mst_set);
- if (cost_so_far + min_rest_cost >= best_so_far) {
- return UINT_MAX;
- }
-
std::sort(temp, temp + toi);
unsigned best_this_cost = UINT_MAX;
if (scanf("%u-%u", &row, &sw) != 2)
break;
+ if (row < MIN_ROW || row > MAX_ROW || sw < MIN_SWITCH || sw > MAX_SWITCH) {
+ fprintf(stderr, "%u-%u is out of bounds!\n", row, sw);
+ exit(1);
+ }
+
points.push_back(std::make_pair(row, sw));
if (points.size() != 1)
points_left.insert(std::make_pair(row, sw));
}
+ // precalculate all distances
+ for (unsigned i = 0; i < points.size(); ++i) {
+ for (unsigned j = 0; j < points.size(); ++j) {
+ cache(points[i].first, points[i].second, 0, points[j].first, points[j].second, 0) =
+ distance(points[i].first, points[i].second, 0, points[j].first, points[j].second, 0);
+
+ cache(points[i].first, points[i].second, 0, points[j].first, points[j].second, 1) =
+ distance(points[i].first, points[i].second, 0, points[j].first, points[j].second, 1);
+
+ cache(points[i].first, points[i].second, 1, points[j].first, points[j].second, 0) =
+ distance(points[i].first, points[i].second, 1, points[j].first, points[j].second, 0);
+
+ cache(points[i].first, points[i].second, 1, points[j].first, points[j].second, 1) =
+ distance(points[i].first, points[i].second, 1, points[j].first, points[j].second, 1);
+
+ opt_cache(points[i].first, points[i].second, points[j].first, points[j].second) =
+ optimistic_distance(points[i].first, points[i].second, points[j].first, points[j].second);
+
+ pess_cache(points[i].first, points[i].second, points[j].first, points[j].second) =
+ pessimistic_distance(points[i].first, points[i].second, points[j].first, points[j].second);
+ }
+ }
+
order *ord = new order[points.size()];
best_tour = new order[points.size()];
order *temp = new order[points.size() * points.size() * 4];
projects / nms / blobdiff