BFS and DFS

2025-04-15 13:36:57 +02:00
parent 8ed7e09075
commit 370adb1234
3 changed files with 140 additions and 0 deletions
--- a/main.py
+++ b/main.py
@@ -0,0 +1,73 @@
+from graph import Graph, Node, Queue
+from utils import getNode
+
+# directed and weighted digraph
+romania = Graph( ['Or', 'Ne', 'Ze', 'Ia', 'Ar', 'Si', 'Fa',
+                  'Va', 'Ri', 'Ti', 'Lu', 'Pi', 'Ur', 'Hi',
+                  'Me', 'Bu', 'Dr', 'Ef', 'Cr', 'Gi'],
+                [
+                    ('Or', 'Ze', 71), ('Or', 'Si', 151),
+                    ('Ne', 'Ia', 87), ('Ze', 'Ar', 75),
+                    ('Ia', 'Va', 92), ('Ar', 'Si', 140),
+                    ('Ar', 'Ti', 118), ('Si', 'Fa', 99),
+                    ('Si', 'Ri', 80), ('Fa', 'Bu', 211),
+                    ('Va', 'Ur', 142), ('Ri', 'Pi', 97),
+                    ('Ri', 'Cr', 146), ('Ti', 'Lu', 111),
+                    ('Lu', 'Me', 70), ('Me', 'Dr', 75),
+                    ('Dr', 'Cr', 120), ('Cr', 'Pi', 138),
+                    ('Pi', 'Bu', 101), ('Bu', 'Gi', 90),
+                    ('Bu', 'Ur', 85), ('Ur', 'Hi', 98),
+                    ('Hi', 'Ef', 86)
+                ] )
+
+def search(graph, queue, start_node_name, target_node_name):
+    cost = 0
+    visited_nodes = []   # Nodes which have been visited
+    path = []
+
+    start_node = getNode(start_node_name, graph.nodes)
+    target_node = getNode(target_node_name, graph.nodes)
+
+    queue.push(start_node)
+
+    while not queue.empty():
+        current_node = queue.pop()
+        visited_nodes.append(current_node.name)
+
+        if current_node == target_node:
+            path.append(current_node.name)
+            tmp = current_node
+            while not tmp == start_node:
+                for edge in tmp.parent.edges:
+                    if edge.end.name == tmp.name:
+                        cost += edge.value
+                tmp = tmp.parent
+                path.insert(0, tmp.name)    # reversed insertion
+        else:
+            for edge in current_node.edges:
+                neighbor = edge.end
+
+                # works with digraph, because current_node is marked at this point, a cycle is not possible
+                if not visited_nodes.__contains__(neighbor.name):
+                    queue.push(neighbor)
+                    neighbor.parent = current_node
+
+    if path.__len__() == 0:
+        print('zwischen ' + start_node_name + ' und ' + target_node_name + ' konnte kein Pfad gefunden werden')
+    else:
+        print('From ' + start_node_name + ' to ' + target_node_name + ': ')
+        print('Path: ' + path.__str__().format())
+        print('Cost: ' + cost.__str__())
+
+def bfs(graph, start_node_name, target_node_name):
+    search(graph,Queue('FIFO'),start_node_name, target_node_name)
+
+def dfs(graph, start_node_name, target_node_name):
+    search(graph,Queue('LIFO'),start_node_name, target_node_name)
+
+def main():
+    bfs(romania, 'Ti', 'Bu')
+    dfs(romania, 'Ti', 'Bu')
+
+if __name__ == "__main__":
+    main()