From 4b0613299db1e9d52eb17c0533b76553ea1300b5 Mon Sep 17 00:00:00 2001
From: Kshitij <kshitijk@tuta.io>
Date: Tue, 8 Oct 2024 19:08:20 +0530
Subject: [PATCH] Added code for assignment B6.

---
 Codes/Code-B6.py | 98 ++++++++++++++++++++++++++++++++++++++++++++++++
 README.md        |  1 +
 2 files changed, 99 insertions(+)
 create mode 100644 Codes/Code-B6.py

diff --git a/Codes/Code-B6.py b/Codes/Code-B6.py
new file mode 100644
index 0000000..da3bd87
--- /dev/null
+++ b/Codes/Code-B6.py
@@ -0,0 +1,98 @@
+import heapq
+
+class LinkStateNetwork:
+  def __init__(self):
+    self.graph = {}
+
+  def add_edge(self, src, dest, weight):
+    if src not in self.graph:
+      self.graph[src] = {}
+    if dest not in self.graph:
+      self.graph[dest] = {}
+      self.graph[src][dest] = weight
+      self.graph[dest][src] = weight  # Undirected graph
+
+  def dijkstra(self, start):
+    distances = {node: float('inf') for node in self.graph}
+    distances[start] = 0
+    priority_queue = [(0, start)]
+    shortest_paths = {node: [] for node in self.graph}
+
+    while priority_queue:
+      current_distance, current_node = heapq.heappop(priority_queue)
+      if current_distance > distances[current_node]:
+        continue
+      for neighbor, weight in self.graph[current_node].items():
+        distance = current_distance + weight
+        if distance < distances[neighbor]:
+          distances[neighbor] = distance
+          shortest_paths[neighbor] = shortest_paths[current_node] + [current_node]
+          heapq.heappush(priority_queue, (distance, neighbor))
+    return distances, shortest_paths
+
+  def print_routing_table(self, start):
+    distances, paths = self.dijkstra(start)
+    print(f"Link-State Routing Table from {start}:")
+    for destination in distances:
+      if distances[destination] < float('inf'):
+        print(f"To {destination} via {' -> '.join(paths[destination] + [destination])}, cost: {distances[destination]}")
+      else:
+        print(f"To {destination}: Unreachable")
+
+# Example usage of Link-State
+if __name__ == "__main__":
+  link_state_network = LinkStateNetwork()
+  link_state_network.add_edge('A', 'B', 1)
+  link_state_network.add_edge('A', 'C', 4)
+  link_state_network.add_edge('B', 'C', 2)
+  link_state_network.add_edge('B', 'D', 5)
+  link_state_network.add_edge('C', 'D', 1)
+  link_state_network.print_routing_table('A')
+
+class DistanceVectorNetwork:
+  def __init__(self):
+    self.graph = {}
+    self.distance_table = {}
+
+  def add_edge(self, src, dest, weight):
+    if src not in self.graph:
+      self.graph[src] = {}
+    if dest not in self.graph:
+      self.graph[dest] = {}
+    self.graph[src][dest] = weight
+    self.graph[dest][src] = weight  # Undirected graph
+
+  def initialize_distance_table(self, start):
+    for node in self.graph:
+      self.distance_table[node] = {n: float('inf') for n in self.graph}
+    self.distance_table[start][start] = 0
+    for neighbor in self.graph[start]:
+      self.distance_table[start][neighbor] = self.graph[start][neighbor]
+
+  def update_distance_table(self):
+    for _ in range(len(self.graph) - 1):
+      for src in self.graph:
+        for dest in self.graph[src]:
+          for neighbor in self.graph[src]:
+            if self.distance_table[src][dest] > self.distance_table[src][neighbor] + self.distance_table[neighbor][dest]:
+              self.distance_table[src][dest] = self.distance_table[src][neighbor] + self.distance_table[neighbor][dest]
+
+  def print_routing_table(self, start):
+    self.initialize_distance_table(start)
+    self.update_distance_table()
+    print(f"Distance Vector Routing Table from {start}:")
+    for destination in self.distance_table[start]:
+      if self.distance_table[start][destination] < float('inf'):
+        print(f"To {destination}: Cost: {self.distance_table[start][destination]}")
+      else:
+        print(f"To {destination}: Unreachable")
+
+# Example usage of Distance Vector
+if __name__ == "__main__":
+  distance_vector_network = DistanceVectorNetwork()
+  distance_vector_network.add_edge('A', 'B', 1)
+  distance_vector_network.add_edge('A', 'C', 4)
+  distance_vector_network.add_edge('B', 'C', 2)
+  distance_vector_network.add_edge('B', 'D', 5)
+  distance_vector_network.add_edge('C', 'D', 1)
+  distance_vector_network.print_routing_table('A')
diff --git a/README.md b/README.md
index c6b3fe2..9e016d2 100644
--- a/README.md
+++ b/README.md
@@ -45,6 +45,7 @@ This Git repository is a comprehensive resource for the Computer Networks and Se
 - [Handout-B5](https://git.kska.io/sppu-te-comp-content/ComputerNetworksAndSecurity/src/branch/main/Handouts/Handout-B5.pdf)
 
 ##### B6 - Link state & distance vector
+- [Code-B6](https://git.kska.io/sppu-te-comp-content/ComputerNetworksAndSecurity/src/branch/main/Codes/Code-B6.py)
 - [Handout-B6](https://git.kska.io/sppu-te-comp-content/ComputerNetworksAndSecurity/src/branch/main/Handouts/Handout-B6.pdf)
 - [Write-up - A6](https://git.kska.io/sppu-te-comp-content/ComputerNetworksAndSecurity/src/branch/main/Write-ups/Write-up%20-%20B6.pdf)
 - [Output-B6](https://git.kska.io/sppu-te-comp-content/ComputerNetworksAndSecurity/src/branch/main/Printable%20outputs/Output-B6.pdf)