more dlx
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@ -7,7 +7,7 @@
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namespace dlx {
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class Dlx {
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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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@ -17,42 +17,18 @@ class Dlx {
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std::size_t s;
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};
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auto LR_self() -> void { L = R = this; }
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auto UD_self() -> void { U = D = this; }
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auto LR_delete() -> void { L->R = R; R->L = L; }
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auto UD_delete() -> void { U->D = D; D->U = U; }
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auto UD_restore() -> void { U->D = D->U = this; }
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auto LR_restore() -> void { L->R = R->L = this; }
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auto LR_insert(Cell* k) -> void { L = k->L; R = k; k->L = k->L->R = this; }
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auto UD_insert(Cell* k) -> void { U = k->U, D = k, k->U = k->U->D = this; }
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static Cell* ColNew() {
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auto c = new Cell;
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c->UD_self();
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c->s = 0;
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return c;
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}
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auto 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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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 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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j->c->s++;
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j->UD_restore();
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}
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}
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LR_restore();
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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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@ -68,6 +44,12 @@ public:
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Dlx();
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~Dlx();
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Dlx(Dlx const&) = delete;
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auto operator=(Dlx const&) -> Dlx& = delete;
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Dlx(Dlx &&);
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auto operator=(Dlx &&) -> Dlx&;
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// Returns number of rows.
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auto Rows() const -> std::size_t;
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@ -82,14 +64,14 @@ public:
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// but it still must respect the constraints it entails.
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auto MarkOptional(std::size_t col) -> void;
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// Removes a row from consideration. Returns 0 on success, -1 otherwise.
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// Removes a row from consideration.
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// Should only be called after all dlx_set() calls.
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auto RemoveRow(std::size_t row) -> int;
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auto RemoveRow(std::size_t row) -> void;
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// Picks a row to be part of the solution. Returns 0 on success, -1 otherwise.
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// Should only be called after all dlx_set() calls and dlx_remove_row() calls.
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// Picks a row to be part of the solution.
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// Should only be called after all Set() calls and RemoveRows() calls.
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// TODO: Check the row can be legally chosen.
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auto PickRow(std::size_t row) -> int;
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auto PickRow(std::size_t row) -> void;
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auto Solve(
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std::function<void(std::size_t, std::size_t, std::size_t)> try_cb,
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156
dlx/src/dlx.cpp
156
dlx/src/dlx.cpp
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@ -4,11 +4,56 @@
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#include <limits>
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using namespace dlx;
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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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auto Dlx::Cell::ColNew() -> Dlx::Cell*
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{
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auto c = new Cell;
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c->UD_self();
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c->s = 0;
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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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{
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auto n = new Cell;
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n->n = row_id;
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n->c = this;
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this->s++;
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n->UD_insert(this);
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return n;
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}
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auto Dlx::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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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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j->c->s++;
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j->UD_restore();
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}
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}
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LR_restore();
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}
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#define F(i,n) for(int i = 0; i < n; i++)
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#define C(i,n,dir) for(cell_ptr i = (n)->dir; i != n; i = i->dir)
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Dlx::Dlx() {
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root_ = Cell::ColNew();
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@ -32,28 +77,39 @@ Dlx::~Dlx() {
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delete root_;
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}
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Dlx::Dlx(Dlx && dlx) : ctab_{}, rtab_{}, root_{}
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{
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std::swap(ctab_, dlx.ctab_);
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std::swap(rtab_, dlx.rtab_);
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std::swap(root_, dlx.root_);
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}
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auto Dlx::operator=(Dlx && dlx) -> Dlx& {
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if (this != &dlx) {
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this->~Dlx();
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new (this) Dlx(std::move(dlx));
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}
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return *this;
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}
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auto Dlx::Rows() const -> std::size_t { return rtab_.size(); }
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auto Dlx::Cols() const -> std::size_t { return ctab_.size(); }
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auto Dlx::AddCol() -> void {
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auto c = Cell::ColNew();
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c->LR_insert(root_);
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c->n = Cols();
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ctab_.push_back(c);
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}
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auto Dlx::AddRow() -> void {
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rtab_.push_back(nullptr);
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}
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auto Dlx::AllocCol(std::size_t n) -> void {
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while(Cols() <= n) AddCol();
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while(Cols() <= n) {
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auto c = Cell::ColNew();
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c->LR_insert(root_);
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c->n = Cols();
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ctab_.push_back(c);
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}
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}
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auto Dlx::AllocRow(std::size_t n) -> void {
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while(Rows() <= n) AddRow();
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while (Rows() <= n) {
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rtab_.push_back(nullptr);
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}
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}
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auto Dlx::MarkOptional(std::size_t col) -> void {
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AllocCol(col);
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auto c = ctab_[col];
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@ -64,29 +120,13 @@ auto Dlx::MarkOptional(std::size_t col) -> void {
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auto Dlx::Set(std::size_t row, std::size_t col) -> void {
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// We don't bother sorting. DLX works fine with jumbled rows and columns.
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// We just have to watch out for duplicates. (Actually, I think the DLX code
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// works even with duplicates, though it would be inefficient.)
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//
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// For a given column, the UD list is ordered in the order that dlx_set()
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// is called, not by row number. Similarly for a given row and its LR list.
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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 const new1 = [&]() -> Cell* {
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auto n = new Cell;
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n->n = row;
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n->c = c;
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c->s++;
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n->UD_insert(c);
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return n;
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};
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auto & r = rtab_[row];
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if (!r) {
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r = new1();
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r = c->ColAdd(row);
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r->LR_self();
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return;
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}
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@ -99,32 +139,28 @@ auto Dlx::Set(std::size_t row, std::size_t col) -> void {
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}
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// Otherwise insert at end of LR list.
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new1()->LR_insert(r);
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c->ColAdd(row)->LR_insert(r);
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}
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auto Dlx::PickRow(std::size_t i) -> int {
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auto r = rtab_.at(i);
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if (!r) return 0; // Empty row.
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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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j->c->CoverCol();
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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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j->c->CoverCol();
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}
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}
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return 0;
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}
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auto Dlx::RemoveRow(std::size_t i) -> int {
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auto & r = rtab_.at(i);
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if (!r) return 0; // Empty row.
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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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j->UD_delete();
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j->c->s--;
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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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j->UD_delete();
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j->c->s--;
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}
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r = nullptr;
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}
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r = nullptr;
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return 0;
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}
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auto Dlx::Solve(
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@ -140,16 +176,16 @@ auto Dlx::Solve(
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return;
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}
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auto s = std::numeric_limits<std::size_t>::max(); // S-heuristic: choose first most-constrained column.
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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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if (i->s < s) {
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s = (c = i)->s;
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}
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}
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if (!s) {
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stuck_cb(c->n);
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return;
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if (s == 0) {
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stuck_cb(c->n);
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return;
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}
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}
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}
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c->CoverCol();
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@ -168,3 +204,5 @@ auto Dlx::Solve(
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};
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recurse(recurse);
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}
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} // namespace
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