| 1 | // -*- C++ -*- |
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| 2 | /* |
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| 3 | *template <Graph, T, Heap=FibHeap> |
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| 4 | * |
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| 5 | *Constructor: |
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| 6 | * |
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| 7 | *Dijkstra(Graph G, NodeIt s, Graph::EdgeMap<T> length) |
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| 8 | * |
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| 9 | * |
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| 10 | *Member functions: |
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| 11 | * |
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| 12 | *void run() |
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| 13 | * |
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| 14 | * The following function should be used after run() was already run. |
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| 15 | * |
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| 16 | *T dist(NodeIt v) : returns the distance from s to v. |
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| 17 | * It is 0 if v is not reachable from s. |
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| 18 | * |
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| 19 | *EdgeIt pred(NodeIt v) : returns the last edge |
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| 20 | * of a shortest s-v path. Returns an invalid iterator |
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| 21 | * if v=s or v is not reachable from s. |
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| 22 | * |
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| 23 | *bool reach(NodeIt v) : true iff v is reachable from s |
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| 24 | * |
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| 25 | */ |
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| 26 | |
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| 27 | #ifndef DIJKSTRA_HH |
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| 28 | #define DIJKSTRA_HH |
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| 29 | |
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| 30 | #include <fib_heap.h> |
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| 31 | |
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| 32 | namespace hugo { |
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| 33 | |
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| 34 | template <typename Graph, typename T, |
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| 35 | typename Heap=FibHeap<typename Graph::NodeIt, T, |
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| 36 | typename Graph::NodeMap<int> > > |
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| 37 | class Dijkstra{ |
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| 38 | typedef typename Graph::NodeIt NodeIt; |
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| 39 | typedef typename Graph::EdgeIt EdgeIt; |
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| 40 | typedef typename Graph::OutEdgeIt OutEdgeIt; |
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| 41 | |
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| 42 | Graph& G; |
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| 43 | NodeIt s; |
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| 44 | typename Graph::NodeMap<EdgeIt> predecessor; |
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| 45 | typename Graph::NodeMap<T> distance; |
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| 46 | typename Graph::EdgeMap<T>& length; |
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| 47 | typename Graph::NodeMap<bool> reached; |
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| 48 | |
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| 49 | public : |
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| 50 | |
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| 51 | /* |
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| 52 | The distance of the nodes is 0. |
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| 53 | */ |
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| 54 | Dijkstra(Graph& _G, NodeIt const _s, |
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| 55 | typename Graph::EdgeMap<T>& _length) : |
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| 56 | G(_G), s(_s), predecessor(G), distance(G), |
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| 57 | length(_length), reached(G, false) { } |
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| 58 | |
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| 59 | |
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| 60 | void run() { |
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| 61 | |
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| 62 | typename Graph::NodeMap<bool> scanned(G, false); |
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| 63 | typename Graph::NodeMap<int> heap_map(G,-1); |
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| 64 | |
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| 65 | Heap heap(heap_map); |
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| 66 | |
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| 67 | heap.push(s,0); |
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| 68 | reached.set(s, true); |
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| 69 | |
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| 70 | while ( !heap.empty() ) { |
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| 71 | |
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| 72 | NodeIt v=heap.top(); |
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| 73 | T oldvalue=heap.get(v); |
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| 74 | heap.pop(); |
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| 75 | distance.set(v, oldvalue); |
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| 76 | |
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| 77 | OutEdgeIt e; |
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| 78 | for( G.getFirst(e,v); G.valid(e); G.next(e)) { |
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| 79 | NodeIt w=G.bNode(e); |
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| 80 | |
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| 81 | if ( !scanned.get(w) ) { |
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| 82 | if ( !reached.get(w) ) { |
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| 83 | reached.set(w,true); |
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| 84 | heap.push(w,oldvalue+length.get(e)); |
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| 85 | predecessor.set(w,e); |
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| 86 | } else if ( oldvalue+length.get(e) < heap.get(w) ) { |
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| 87 | predecessor.set(w,e); |
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| 88 | heap.decrease(w, oldvalue+length.get(e)); |
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| 89 | } |
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| 90 | } |
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| 91 | } |
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| 92 | scanned.set(v,true); |
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| 93 | } |
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| 94 | } |
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| 95 | |
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| 96 | |
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| 97 | T dist(NodeIt v) { |
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| 98 | return distance.get(v); |
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| 99 | } |
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| 100 | |
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| 101 | |
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| 102 | EdgeIt pred(NodeIt v) { |
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| 103 | if ( v!=s ) return predecessor.get(v); |
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| 104 | else return EdgeIt(); |
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| 105 | } |
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| 106 | |
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| 107 | |
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| 108 | bool reach(NodeIt v) { |
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| 109 | return reached.get(v); |
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| 110 | } |
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| 111 | |
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| 112 | }; |
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| 113 | |
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| 114 | } |
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| 115 | |
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| 116 | #endif |
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| 117 | |
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| 118 | |
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