Какой алгоритм реализует приведенная ниже программа?
type vertices = ^vertex; edges = ^edge; vertex = record id,dist: integer; incidence: edges; next: vertices; end; edge = record from,toward: vertices; len: integer; next: edges; end; ptr_edges = ^ptr_edge; ptr_edge = record e: edges; next: ptr_edges; end;var i,j,len,source_id: integer; g,source: vertices; queue,head,next_head: ptr_edges; f: text;function new_vertex(i: integer; g: vertices): vertices;var v: vertices;begin new(v); v^.id:= i; v^.dist:= maxint; v^.incidence:= nil; v^.next:= g; new_vertex:= vend;function find_vertex(i: integer; g: vertices): vertices;var v: vertices;begin v:= g; while (v<>nil)and(v^.id<>i) do v:= v^.next; find_vertex:= vend;function find_edge(j: integer; n: edges): edges;var e: edges;begin e:= n; while (e<>nil)and(e^.toward^.id<>j) do e:= e^.next; find_edge:= eend;procedure new_edge(i,j,len: integer; var g: vertices);var vi,vj: vertices; eij: edges;begin vi:= find_vertex(i,g); if vi = nil then begin g:= new_vertex(i,g); vi:= g end; vj:= find_vertex(j,g); if vj = nil then begin g:= new_vertex(j,g); vj:= g end; eij:= find_edge(j,vi^.incidence); if eij = nil then begin new(eij); eij^.from:= vi; eij^.toward:= vj; eij^.len:= len; eij^.next:= vi^.incidence; vi^.incidence:= eij endend;procedure enqueue(v: vertices; var q,h: ptr_edges);var e: edges; pe: ptr_edges;begin e:= v^.incidence; while e<>nil do begin new(pe); pe^.e:= e; pe^.next:= nil; if q = nil then h:= pe else q^.next:= pe; q:= pe; e:= e^.next endend;procedure print_vertices(g: vertices);var v: vertices;begin v:= g; while v<>nil do begin writeln(source_id,' -> ',v^.id,' : ',v^.dist); v:= v^.next endend;procedure dispose_edges(n: edges);var e,e_next: edges;begin e:= n; while e<>nil do begin e_next:= e^.next; dispose(e); e:= e_next endend;procedure dispose_vertices(g: vertices);var v,v_next: vertices;begin v:= g; while v<>nil do begin v_next:= v^.next; dispose_edges(v^.incidence); dispose(v); v:= v_next; end;end;begin assign(f,'in'); reset(f); readln(f,source_id); {в первой строке записана начальная вершина} g:= nil; while not eof(f) do begin readln(f,i,j,len); {граф задан списком ребер: от, до, длина} new_edge(i,j,len,g); new_edge(j,i,len,g); end; source:= find_vertex(source_id,g); source^.dist:= 0; queue:= nil; head:= nil; enqueue(source,queue,head); while head<>nil do begin with head^.e^ do if from^.dist+len < toward^.dist then begin toward^.dist:= from^.dist + len; enqueue(toward,queue,head); end; next_head:= head ^.next; dispose(head); head:= next_head end; print_vertices(g); dispose_vertices(g);end.
