From c05b52762f157760355e7a332dab345a75daf83f Mon Sep 17 00:00:00 2001
From: abhaysinghraihal <117754689+abhaysinghraihal@users.noreply.github.com>
Date: Sun, 15 Jan 2023 11:41:12 +0530
Subject: [PATCH] Python implementation for greedy graph colouring algo

---
 algorithms/graph/greedyGraphColoring.py | 64 +++++++++++++++++++++++++
 1 file changed, 64 insertions(+)
 create mode 100644 algorithms/graph/greedyGraphColoring.py

diff --git a/algorithms/graph/greedyGraphColoring.py b/algorithms/graph/greedyGraphColoring.py
new file mode 100644
index 000000000..44b3a9e56
--- /dev/null
+++ b/algorithms/graph/greedyGraphColoring.py
@@ -0,0 +1,64 @@
+
+def addEdge(adj, v, w):
+	
+	adj[v].append(w)
+	
+	# Note: the graph is undirected
+	adj[w].append(v)
+	return adj
+
+# Assigns colors (starting from 0) to all
+# vertices and prints the assignment of colors
+def greedyColoring(adj, V):
+	
+	result = [-1] * V
+	result[0] = 0;
+
+
+	available = [False] * V
+
+	for u in range(1, V):
+		
+		for i in adj[u]:
+			if (result[i] != -1):
+				available[result[i]] = True
+
+		cr = 0
+		while cr < V:
+			if (available[cr] == False):
+				break
+			
+			cr += 1
+			
+		result[u] = cr
+
+		for i in adj[u]:
+			if (result[i] != -1):
+				available[result[i]] = False
+
+	for u in range(V):
+		print("Vertex", u, " ---> Color", result[u])
+
+# Driver Code
+if __name__ == '__main__':
+	
+	g1 = [[] for i in range(5)]
+	g1 = addEdge(g1, 0, 1)
+	g1 = addEdge(g1, 0, 2)
+	g1 = addEdge(g1, 1, 2)
+	g1 = addEdge(g1, 1, 3)
+	g1 = addEdge(g1, 2, 3)
+	g1 = addEdge(g1, 3, 4)
+	print("Coloring of graph 1 ")
+	greedyColoring(g1, 5)
+
+	g2 = [[] for i in range(5)]
+	g2 = addEdge(g2, 0, 1)
+	g2 = addEdge(g2, 0, 2)
+	g2 = addEdge(g2, 1, 2)
+	g2 = addEdge(g2, 1, 4)
+	g2 = addEdge(g2, 2, 4)
+	g2 = addEdge(g2, 4, 3)
+	print("\nColoring of graph 2")
+	greedyColoring(g2, 5)
+