challenge 38

README.md

@@ -28,7 +28,8 @@
 |33|hashmap-left-join|[hashmap-left-join](./challenges/hash_table/hashmap-left-join/README.md)|
 |35|Graphs|[Graphs](./data-structures/graph/README.md)|
 |36|Graphs-breadth-first|[Graphs-breadth-first](./data-structures/graph/README_BF.md)|
-|37|graph-business-trip|[graph-business-trip](./data-structures/graph/graph_business_trip/README.md)|
+|37|graph-business-trip|[graph-business-trip](./challenges/graph/graph_business_trip/README.md)|
+|38|graph-depth-first|[graph-depth-first](./data-structures/graph/README_DF.md)|
 
 
 

data-structures/graph/README_DF.md

@@ -0,0 +1,20 @@
+# Challenge Summary
+create function  that takes node as input and return all nodes exists in graph in depth first order
+
+## Whiteboard Process
+![image](./assets/challenge-38-graph-depth-first.png)
+
+## Approach & Efficiency
+time:O(n)
+space:O(n)
+
+## Solution
+- declare empty set(visited)
+- declare empty queue
+- enqueue the starting node
+- create while loop and the condition that if the queue is not empty
+- dequeue the node from the queue to the variable (current)
+- add current to the set(visited)
+- get the neighbors of the current
+- enqueue the neighbors if its not in the set(visited)
+- after the while return the nodes array

data-structures/graph/graph/graph.py

@@ -1,6 +1,6 @@
 import sys
 sys.path.append("/home/bayan/code-401/data-structures-and-algorithms-401/data-structures/stack_and_queue")
-from stack_and_queue.stack_and_queue import Queue
+from stack_and_queue.stack_and_queue import Queue, Stack
 
 class Node:
     def __init__(self, value):
@@ -76,6 +76,28 @@ def breadth_first(self, node):
 
         return nodes
 
+    def depth_first(self, node):
+        nodes=[]
+        stack= Stack()
+        visited= set()
+
+        if node not in self.adjacency_list or self.adjacency_list[node]==[]:
+            return None
+
+        stack.push(node)
+        visited.add(node.value)
+
+        while not stack.isEmpty():
+            vertix=stack.pop()
+            nodes.append(vertix.value)
+
+            for edge in self.adjacency_list[vertix]:
+                if  edge.node.value not in visited:
+                    visited.add(edge.node.value)
+                    stack.push(edge.node)
+
+        return nodes
+
 
 
 if __name__ == '__main__':
@@ -108,7 +130,7 @@ def breadth_first(self, node):
     # graph.add_edge(a,b,5)
     # graph.add_edge(a,c,7)
     # print(graph.breadth_first(b))
-    print (graph)
+    print (graph.depth_first(e))
 
 
 

data-structures/graph/tests/test_graph.py

@@ -72,6 +72,15 @@ def test_breadth_first(graph_3):
     actual=graph_3[0].breadth_first(graph_3[1])
     assert actual == expected 
 
+def test_depth_first(graph_3):
+    expected=['b', 'f', 'e', 'd', 'a', 'c']
+    actual=graph_3[0].depth_first(graph_3[1])
+    assert actual == expected 
+
+def test_depth_first1(graph_3):
+    expected=['e', 'f', 'b', 'd', 'a', 'c']
+    actual=graph_3[0].depth_first(graph_3[2])
+    assert actual == expected 
 
 
 @pytest.fixture
@@ -124,4 +133,4 @@ def graph_3():
     graph.add_edge(f, b)
     graph.add_edge(f, e) 
 
-    return graph, b
+    return graph, b, e