From 176c33092544eb0ab7f37b0aa17094848140f985 Mon Sep 17 00:00:00 2001
From: arpanjain97 <arpanjain97@gmail.com>
Date: Fri, 13 Oct 2017 11:31:06 +0530
Subject: [PATCH] Add Bellman-Ford Algorithm

---
 data_structures/Graph/BellmanFord.py | 52 ++++++++++++++++++++++++++++
 1 file changed, 52 insertions(+)
 create mode 100644 data_structures/Graph/BellmanFord.py

diff --git a/data_structures/Graph/BellmanFord.py b/data_structures/Graph/BellmanFord.py
new file mode 100644
index 000000000..de3077f09
--- /dev/null
+++ b/data_structures/Graph/BellmanFord.py
@@ -0,0 +1,52 @@
+def printDist(dist, V):
+	print("\nVertex Distance")
+	for i in range(V):
+		if dist[i] != float('inf') :
+			print(i,"\t",int(dist[i]),end = "\t")
+		else:
+			print(i,"\t","INF",end="\t")
+		print();
+
+def BellmanFord(graph, V, E, src):
+	mdist=[float('inf') for i in range(V)]
+	mdist[src] = 0.0;
+	
+	for i in range(V-1):
+		for j in range(V):
+			u = graph[j]["src"]
+			v = graph[j]["dst"]
+			w = graph[j]["weight"]
+
+			if mdist[u] != float('inf') and mdist[u] + w < mdist[v]:
+				mdist[v] = mdist[u] + w 
+	for j in range(V):
+			u = graph[j]["src"]
+			v = graph[j]["dst"]
+			w = graph[j]["weight"]
+
+			if mdist[u] != float('inf') and mdist[u] + w < mdist[v]:
+				print("Negative cycle found. Solution not possible.")
+				return
+	
+	printDist(mdist, V)	
+
+			
+
+#MAIN
+V = int(input("Enter number of vertices: "));
+E = int(input("Enter number of edges: "));
+
+graph = [dict() for j in range(E)]
+
+for i in range(V):
+	graph[i][i] = 0.0;
+
+for i in range(E):
+	print("\nEdge ",i+1)
+	src = int(input("Enter source:"))
+	dst = int(input("Enter destination:"))
+	weight = float(input("Enter weight:"))
+	graph[i] = {"src": src,"dst": dst, "weight": weight}
+	
+gsrc = int(input("\nEnter shortest path source:"))
+BellmanFord(graph, V, E, gsrc)