Implementation of Dijkstra with adjacency list and priority queue in Ruby

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require 'pqueue'
def dijkstra(source, edges, num_vertices)
 path_weights = Array.new(num_vertices, Float::INFINITY)
 previous_shortest_path = Array.new(num_vertices, nil)
 pq = PQueue.new([source])x,y
 path_weights[source] = 0

 while pq.size != 0
 min_node = pq.pop
 # Note: If we are interested only in shortest distance from source to a single target, we can break the for loop when the picked minimum distance vertex is equal to target

 (edges[min_node] || ).each do |neighbor, weight|
 if path_weights[neighbor] > path_weights[min_node] + weight
 path_weights[neighbor] = path_weights[min_node] + weight
 previous_shortest_path[neighbor] = min_node
 pq.push(neighbor)
 end
 end
 end

 return [path_weights, previous_shortest_path]
end

Assuming that the priority queue uses a binary heap, this should be O(E log V)

Would this work for all graphs without negative cycles? Any obvious improvements or edge cases missing?

edited May 14 at 4:24

Mast

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asked May 13 at 22:03

bgcode

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require 'pqueue'
def dijkstra(source, edges, num_vertices)
 path_weights = Array.new(num_vertices, Float::INFINITY)
 previous_shortest_path = Array.new(num_vertices, nil)
 pq = PQueue.new([source])x,y
 path_weights[source] = 0

 while pq.size != 0
 min_node = pq.pop
 # Note: If we are interested only in shortest distance from source to a single target, we can break the for loop when the picked minimum distance vertex is equal to target

 (edges[min_node] || ).each do |neighbor, weight|
 if path_weights[neighbor] > path_weights[min_node] + weight
 path_weights[neighbor] = path_weights[min_node] + weight
 previous_shortest_path[neighbor] = min_node
 pq.push(neighbor)
 end
 end
 end

 return [path_weights, previous_shortest_path]
end

Assuming that the priority queue uses a binary heap, this should be O(E log V)

Would this work for all graphs without negative cycles? Any obvious improvements or edge cases missing?

edited May 14 at 4:24

Mast

7,32563484

asked May 13 at 22:03

bgcode

1012

add a commentÂ |Â

up vote
0
down vote

favorite

require 'pqueue'
def dijkstra(source, edges, num_vertices)
 path_weights = Array.new(num_vertices, Float::INFINITY)
 previous_shortest_path = Array.new(num_vertices, nil)
 pq = PQueue.new([source])x,y
 path_weights[source] = 0

 while pq.size != 0
 min_node = pq.pop
 # Note: If we are interested only in shortest distance from source to a single target, we can break the for loop when the picked minimum distance vertex is equal to target

 (edges[min_node] || ).each do |neighbor, weight|
 if path_weights[neighbor] > path_weights[min_node] + weight
 path_weights[neighbor] = path_weights[min_node] + weight
 previous_shortest_path[neighbor] = min_node
 pq.push(neighbor)
 end
 end
 end

 return [path_weights, previous_shortest_path]
end

Assuming that the priority queue uses a binary heap, this should be O(E log V)

Would this work for all graphs without negative cycles? Any obvious improvements or edge cases missing?

edited May 14 at 4:24

Mast

7,32563484

asked May 13 at 22:03

bgcode

1012

require 'pqueue'
def dijkstra(source, edges, num_vertices)
 path_weights = Array.new(num_vertices, Float::INFINITY)
 previous_shortest_path = Array.new(num_vertices, nil)
 pq = PQueue.new([source])x,y
 path_weights[source] = 0

 while pq.size != 0
 min_node = pq.pop
 # Note: If we are interested only in shortest distance from source to a single target, we can break the for loop when the picked minimum distance vertex is equal to target

 (edges[min_node] || ).each do |neighbor, weight|
 if path_weights[neighbor] > path_weights[min_node] + weight
 path_weights[neighbor] = path_weights[min_node] + weight
 previous_shortest_path[neighbor] = min_node
 pq.push(neighbor)
 end
 end
 end

 return [path_weights, previous_shortest_path]
end

Assuming that the priority queue uses a binary heap, this should be O(E log V)

Would this work for all graphs without negative cycles? Any obvious improvements or edge cases missing?

edited May 14 at 4:24

Mast

7,32563484

asked May 13 at 22:03

bgcode

1012

edited May 14 at 4:24

Mast

7,32563484

edited May 14 at 4:24

Mast

7,32563484

edited May 14 at 4:24

Mast

7,32563484

asked May 13 at 22:03

bgcode

1012

asked May 13 at 22:03

bgcode

1012

asked May 13 at 22:03

bgcode

1012

add a commentÂ |Â

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