Merge pull request #648 from sriharsha200/my-techdoc-contribution

Graph traversal BFS and DFS in Python

Author: singhanshika311

Data Structures/Graphs/BFS.py

@@ -0,0 +1,33 @@
+#  BFS Traversal of Graph using Adjacency Matrix Representation 
+#  Function To implement BFS (Breath First Search)
+def Breathfirstsearch(matrix,start):
+    visit=[start] #Keep Track of Visited Vertex
+    queue=[start] #BFS is implemented using queue
+    while(len(queue)) :
+        ele=queue.pop(0) #pop the element from queue ie first element from list
+        for i in range(len(matrix)):
+            if matrix[ele][i]==1 and i not in visit: # check the adjacent elements and push into the queue if the vertix was not visited
+                  visit.append(i)
+                  queue.append(i)
+    return visit
+def valid(li,n): 
+    if len(li)==n: #each row should contain n elements
+        for i in li: 
+            if i!=0 and i!=1: #each row should contain 0's and 1's 
+                return False
+    return True
+# main function
+if __name__ == "__main__":
+     n=int(input("Enter the no of vertices\n")) # Read no of vertices
+     print("Enter adjacency matrix of graph") # Read adjacency matrix
+     matrix=[]
+     for _ in range(n):
+         li=list(map(int,input().split()))
+         if(valid(li,n)==False): # check wheather the given list is in valid adjacency matrix or not should contain 0's and 1's
+             print("Enter valid n*n matrix")
+             exit # Terminate the program for incorrect details
+         matrix.append(li)   
+     start=int(input("Enter the starting vertix\n"))
+     ans=Breathfirstsearch(matrix,start) 
+     print("BFS order of the given graph is ",end=" ")
+     print(*ans)  

Data Structures/Graphs/DFS.PY

@@ -0,0 +1,35 @@
+#  DFS Traversal of Graph using Adjacency Matrix Representation 
+#  Function To implement DFS (Depth First Search)
+def Depthfirstsearch(matrix,start):
+    visit=[start] #Keep Track of Visited elements
+    stack=[start] #DFS is implemented using stack
+    while(len(stack)) :
+        ele=stack.pop(-1) #pop the element from stack ie last element from list
+        for i in range(len(matrix)):
+            if matrix[ele][i]==1 and i not in visit: # check the adjacent elements and push into the stack if the vertix was not visited
+                  stack.append(ele)
+                  visit.append(i)
+                  stack.append(i) 
+                  break
+    return visit
+def valid(li,n): 
+    if len(li)==n: #each row should contain n elements
+        for i in li: 
+            if i!=0 and i!=1: #each row should contain 0's and 1's 
+                return False
+    return True
+# main function
+if __name__ == "__main__":
+     n=int(input("Enter the no of vertices\n")) # Read no of vertices
+     print("Enter adjacency matrix of graph") # Read adjacency matrix
+     matrix=[]
+     for _ in range(n):
+         li=list(map(int,input().split()))
+         if(valid(li,n)==False): # check wheather the given list is in valid adjacency matrix or not should contain 0's and 1's
+             print("Enter valid n*n matrix")
+             exit # Terminate the program for incorrect details
+         matrix.append(li)   
+     start=int(input("Enter the starting vertix\n"))
+     ans=Depthfirstsearch(matrix,start)
+     print("DFS of the given graph is ",end=" ")
+     print(*ans)