Dijkstra 法の Fibonacci Heap を用いた高速化 と同様の手法で prim 法の計算量も $\O (n \log n + m)$ に落ちる.
元論文は "Fibonacci Heaps and Their Uses in Improved Network Optimization Algorithms" [Fredman, Tarjan 1984]
時間計算量: $\O (n \log n + m)$
- template<typename _Key, typename _Tp> class FibonacciHeap
- {
- public:
- using data_type = pair<_Key, _Tp>;
- class node
- {
- public:
- data_type _data;
- unsigned short int _child;
- bool _mark;
- node *_par, *_prev, *_next, *_ch_last;
- node(data_type&& data) : _data(move(data)), _child(0), _mark(false),
- _par(nullptr), _prev(nullptr), _next(nullptr), _ch_last(nullptr){}
- inline const _Key& get_key() const noexcept { return _data.first; }
- void insert(node *cur){
- if(_ch_last) insert_impl(cur, _ch_last);
- else _ch_last = cur, _ch_last->_prev = _ch_last->_next = _ch_last;
- ++_child, cur->_par = this;
- }
- void erase(node *cur){
- if(cur == cur->_prev){
- _ch_last = nullptr;
- }else{
- erase_impl(cur);
- if(cur == _ch_last) _ch_last = cur->_prev;
- }
- --_child, cur->_par = nullptr;
- }
- };
- private:
- size_t _size;
- node *_minimum;
- vector<node*> rank;
- static void insert_impl(node *cur, node *next){
- cur->_prev = next->_prev, cur->_next = next;
- cur->_prev->_next = cur, next->_prev = cur;
- }
- static void erase_impl(node *cur){
- cur->_prev->_next = cur->_next, cur->_next->_prev = cur->_prev;
- }
- void root_insert(node *cur){
- if(_minimum){
- insert_impl(cur, _minimum);
- if(cur->get_key() < _minimum->get_key()) _minimum = cur;
- }else{
- _minimum = cur, _minimum->_prev = _minimum->_next = _minimum;
- }
- }
- void root_erase(node *cur){
- if(cur == cur->_prev) _minimum = nullptr;
- else erase_impl(cur);
- }
- void _delete(node *cur){
- root_erase(cur);
- delete cur;
- }
- template<typename Key, typename Data>
- node *_push(Key&& key, Data&& data){
- ++_size;
- data_type new_data(forward<Key>(key), forward<Data>(data));
- node* new_node = new node(move(new_data));
- root_insert(new_node);
- return new_node;
- }
- void _pop(){
- assert(_size > 0);
- --_size;
- if(_size == 0){
- _delete(_minimum);
- return;
- }
- if(_minimum->_ch_last){
- for(node *cur = _minimum->_ch_last->_next;;){
- node *next = cur->_next;
- _minimum->erase(cur), root_insert(cur);
- if(!_minimum->_ch_last) break;
- cur = next;
- }
- }
- node *next_minimum = _minimum->_next;
- for(node*& cur : rank) cur = nullptr;
- for(node *cur = next_minimum; cur != _minimum;){
- if(cur->get_key() < next_minimum->get_key()) next_minimum = cur;
- node *next = cur->_next;
- unsigned int deg = cur->_child;
- if(rank.size() <= deg) rank.resize(deg + 1, nullptr);
- while(rank[deg]){
- if(cur->get_key() < rank[deg]->get_key() || cur == next_minimum){
- root_erase(rank[deg]), cur->insert(rank[deg]);
- }else{
- root_erase(cur), rank[deg]->insert(cur);
- cur = rank[deg];
- }
- rank[deg++] = nullptr;
- if(rank.size() <= deg) rank.resize(deg + 1, nullptr);
- }
- rank[deg] = cur;
- cur = next;
- }
- _delete(_minimum);
- _minimum = next_minimum;
- }
- void _decrease_key(node *cur, const _Key& key){
- assert(!(key < (_Key)0));
- node *change = ((cur->_data.first -= key) < _minimum->get_key()) ? cur : nullptr;
- if(!cur->_par || !(cur->get_key() < cur->_par->get_key())){
- if(change) _minimum = change;
- return;
- }
- while(true){
- node *next = cur->_par;
- next->erase(cur), root_insert(cur);
- cur->_mark = false, cur = next;
- if(!cur->_par) break;
- if(!cur->_mark){
- cur->_mark = true;
- break;
- }
- }
- if(change) _minimum = change;
- }
- void clear_dfs(node *cur){
- if(cur->_ch_last){
- for(node *_cur = cur->_ch_last->_next;;){
- node *next = _cur->_next;
- if(_cur == cur->_ch_last){
- clear_dfs(_cur);
- break;
- }else{
- clear_dfs(_cur);
- }
- _cur = next;
- }
- }
- delete cur;
- return;
- }
- void _clear(){
- if(!_minimum) return;
- for(node *cur = _minimum->_next;;){
- node *next = cur->_next;
- if(cur == _minimum){
- clear_dfs(cur);
- break;
- }else{
- clear_dfs(cur);
- }
- cur = next;
- }
- }
- public:
- FibonacciHeap() noexcept : _size(0u), _minimum(nullptr){}
- // ~FibonacciHeap(){ _clear(); }
- inline bool empty() const noexcept { return (_size == 0); }
- inline size_t size() const noexcept { return _size; }
- inline const data_type& top() const noexcept { return _minimum->_data; }
- template<typename Key, typename Data>
- node *push(Key&& key, Data&& data){ return _push(forward<Key>(key), forward<Data>(data)); }
- void pop(){ _pop(); }
- void decrease_key(node *cur, const _Key& key){ _decrease_key(cur, key); }
- void clear(){ _clear(); _size = 0; rank.~vector<node*>(); }
- };
- template<typename T> class Prim {
- public:
- struct edge{
- int to;
- T cost;
- };
- const int V;
- const T inf = numeric_limits<T>::max();
- vector<vector<edge> > G;
- vector<T> d;
- FibonacciHeap<T, int> fheap;
- vector<typename FibonacciHeap<T, int>::node*> nodes;
- Prim(int node_size)
- : V(node_size), G(V), d(V, inf), fheap(), nodes(V, nullptr){}
- void add_edge(int u, int v, T val){
- G[u].push_back((edge){v, val}), G[v].push_back((edge){u, val});
- }
- T solve(){
- T res = 0;
- d[0] = 0;
- nodes[0] = fheap.push(0, 0);
- while(!fheap.empty()){
- const int v = fheap.top().second;
- res += fheap.top().first;
- fheap.pop();
- d[v] = -1;
- for(auto& e : G[v]){
- if(d[e.to] >= 0 && d[e.to] > e.cost){
- if(d[e.to] == inf){
- nodes[e.to] = fheap.push(e.cost, e.to);
- }else{
- fheap.decrease_key(nodes[e.to], d[e.to] - e.cost);
- }
- d[e.to] = e.cost;
- }
- }
- }
- return res;
- }
- };