dlx: nicer iteration
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50640e6adb
commit
234165c7f3
@ -7,30 +7,9 @@
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namespace dlx {
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struct Cell;
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class Dlx final {
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struct Cell {
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Cell *U, *D, *L, *R;
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std::size_t n;
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union {
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Cell* c;
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std::size_t s;
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};
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auto LR_self() -> void;
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auto UD_self() -> void;
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auto LR_delete() -> void;
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auto UD_delete() -> void;
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auto UD_restore() -> void;
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auto LR_restore() -> void;
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auto LR_insert(Cell* k) -> void;
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auto UD_insert(Cell* k) -> void;
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auto CoverCol() -> void;
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auto UncoverCol() -> void;
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auto ColAdd(std::size_t row_id) -> Cell*;
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static Cell* ColNew();
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};
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std::vector<Cell*> ctab_;
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std::vector<Cell*> rtab_;
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Cell* root_;
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130
dlx/src/dlx.cpp
130
dlx/src/dlx.cpp
@ -6,16 +6,76 @@
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namespace dlx {
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auto Dlx::Cell::LR_self() -> void { L = R = this; }
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auto Dlx::Cell::UD_self() -> void { U = D = this; }
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auto Dlx::Cell::LR_delete() -> void { L->R = R; R->L = L; }
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auto Dlx::Cell::UD_delete() -> void { U->D = D; D->U = U; }
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auto Dlx::Cell::UD_restore() -> void { U->D = D->U = this; }
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auto Dlx::Cell::LR_restore() -> void { L->R = R->L = this; }
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auto Dlx::Cell::LR_insert(Cell* k) -> void { L = k->L; R = k; k->L = k->L->R = this; }
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auto Dlx::Cell::UD_insert(Cell* k) -> void { U = k->U, D = k, k->U = k->U->D = this; }
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template <Cell* Cell::* direction> struct CellView;
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auto Dlx::Cell::ColNew() -> Dlx::Cell*
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struct Cell {
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Cell *U, *D, *L, *R;
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std::size_t n;
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union {
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Cell* c;
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std::size_t s;
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};
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auto LR_self() -> void;
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auto UD_self() -> void;
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auto LR_delete() -> void;
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auto UD_delete() -> void;
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auto UD_restore() -> void;
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auto LR_restore() -> void;
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auto LR_insert(Cell* k) -> void;
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auto UD_insert(Cell* k) -> void;
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auto CoverCol() -> void;
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auto UncoverCol() -> void;
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auto rightwards() -> CellView<&Cell::R>;
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auto leftwards() -> CellView<&Cell::L>;
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auto upwards() -> CellView<&Cell::U>;
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auto downwards() -> CellView<&Cell::D>;
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auto ColAdd(std::size_t row_id) -> Cell*;
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static Cell* ColNew();
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};
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template <Cell* Cell::* direction>
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struct CellView {
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Cell* cell;
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auto operator==(CellView const&) const -> bool = default;
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auto begin() const -> CellView;
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auto end() const -> CellView;
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auto operator*() -> Cell*;
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auto operator++() -> CellView&;
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};
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template <Cell* Cell::* direction>
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auto CellView<direction>::begin() const -> CellView { return {cell->*direction}; }
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template <Cell* Cell::* direction>
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auto CellView<direction>::end() const -> CellView { return {cell}; }
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template <Cell* Cell::* direction>
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auto CellView<direction>::operator*() -> Cell* { return cell; }
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template <Cell* Cell::* direction>
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auto CellView<direction>::operator++() -> CellView& {
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cell = cell->*direction;
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return *this;
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}
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auto Cell::LR_self() -> void { L = R = this; }
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auto Cell::UD_self() -> void { U = D = this; }
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auto Cell::LR_delete() -> void { L->R = R; R->L = L; }
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auto Cell::UD_delete() -> void { U->D = D; D->U = U; }
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auto Cell::UD_restore() -> void { U->D = D->U = this; }
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auto Cell::LR_restore() -> void { L->R = R->L = this; }
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auto Cell::LR_insert(Cell* k) -> void { L = k->L; R = k; k->L = k->L->R = this; }
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auto Cell::UD_insert(Cell* k) -> void { U = k->U, D = k, k->U = k->U->D = this; }
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auto Cell::ColNew() -> Cell*
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{
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auto c = new Cell;
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c->UD_self();
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@ -23,7 +83,7 @@ auto Dlx::Cell::ColNew() -> Dlx::Cell*
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return c;
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}
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auto Dlx::Cell::ColAdd(std::size_t row_id) -> Cell*
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auto Cell::ColAdd(std::size_t row_id) -> Cell*
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{
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auto n = new Cell;
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n->n = row_id;
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@ -33,19 +93,19 @@ auto Dlx::Cell::ColAdd(std::size_t row_id) -> Cell*
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return n;
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}
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auto Dlx::Cell::CoverCol() -> void {
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auto Cell::CoverCol() -> void {
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LR_delete();
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for (auto i = D; i != this; i = i->D) {
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for (auto j = i->R; j != i; j = j->R) {
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for (auto const i : downwards()) {
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for (auto const j : i->rightwards()) {
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j->UD_delete();
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j->c->s--;
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}
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}
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}
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auto Dlx::Cell::UncoverCol() -> void {
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for (auto i = U; i != this; i = i->U) {
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for (auto j = i->L; j != i; j = j->L) {
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auto Cell::UncoverCol() -> void {
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for (auto const i : upwards()) {
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for (auto const j : i->leftwards()) {
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j->c->s++;
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j->UD_restore();
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}
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@ -53,7 +113,10 @@ auto Dlx::Cell::UncoverCol() -> void {
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LR_restore();
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}
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auto Cell::rightwards() -> CellView<&Cell::R> { return CellView<&Cell::R>{this}; }
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auto Cell::leftwards() -> CellView<&Cell::L> { return CellView<&Cell::L>{this}; }
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auto Cell::upwards() -> CellView<&Cell::U> { return CellView<&Cell::U>{this}; }
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auto Cell::downwards() -> CellView<&Cell::D> { return CellView<&Cell::D>{this}; }
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Dlx::Dlx() {
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root_ = Cell::ColNew();
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@ -63,16 +126,18 @@ Dlx::Dlx() {
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Dlx::~Dlx() {
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for (auto const row : rtab_) {
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if (row) {
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Cell* next;
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for (auto cursor = row->R; cursor != row; cursor = next) {
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next = cursor->R;
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delete cursor;
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auto cursor = row->R;
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// manual iteration because we have to save next _before_ deleting cursor
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while (cursor != row) {
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auto tmp = cursor;
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cursor = cursor->R;
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delete tmp;
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}
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delete row;
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}
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}
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for (auto const col : ctab_) {
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if (col) { delete col; }
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delete col;
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}
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delete root_;
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}
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@ -118,13 +183,12 @@ auto Dlx::MarkOptional(std::size_t col) -> void {
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c->LR_self();
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}
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auto Dlx::Set(std::size_t row, std::size_t col) -> void {
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AllocRow(row);
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AllocCol(col);
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auto c = ctab_[col];
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auto c = ctab_[col];
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auto & r = rtab_[row];
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if (!r) {
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r = c->ColAdd(row);
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r->LR_self();
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@ -134,7 +198,7 @@ auto Dlx::Set(std::size_t row, std::size_t col) -> void {
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// Ignore duplicates.
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if (r->c->n == col) return;
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for (auto cursor = r->R; cursor != r; cursor = cursor->R) {
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for (auto const cursor : r->rightwards()) {
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if (cursor->c->n == col) return;
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}
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@ -145,7 +209,7 @@ auto Dlx::Set(std::size_t row, std::size_t col) -> void {
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auto Dlx::PickRow(std::size_t i) -> void {
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if (auto r = rtab_.at(i)) {
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r->c->CoverCol();
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for (auto j = r->R; j != r; j = j->R) {
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for (auto const j : r->rightwards()) {
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j->c->CoverCol();
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}
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}
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@ -155,7 +219,7 @@ auto Dlx::RemoveRow(std::size_t i) -> void {
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if (auto & r = rtab_.at(i)) {
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r->UD_delete();
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r->c->s--;
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for (auto j = r->R; j != r; j = j->R) {
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for (auto const j : r->rightwards()) {
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j->UD_delete();
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j->c->s--;
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}
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@ -177,10 +241,10 @@ auto Dlx::Solve(
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}
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auto s = std::numeric_limits<std::size_t>::max();
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for (auto i = root_->R; i != root_; i = i->R) {
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for (auto const i : root_->rightwards()) {
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if (i->s < s) {
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s = (c = i)->s;
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if (s == 0) {
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stuck_cb(c->n);
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return;
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@ -189,14 +253,14 @@ auto Dlx::Solve(
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}
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c->CoverCol();
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for (auto r = c->D; r != c; r = r->D) {
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for (auto const r : c->downwards()) {
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try_cb(c->n, s, r->n);
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for (auto j = r->R; j != r; j = j->R) {
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for (auto const j : r->rightwards()) {
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j->c->CoverCol();
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}
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self(self);
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undo_cb();
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for (auto j = r->L; j != r; j=j->L) {
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for (auto const j : r->leftwards()) {
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j->c->UncoverCol();
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}
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}
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