Question

Please write a python function for :

greedy: This function takes two inputs: one a graph, and the other an ordering of the vertices as a list, and returns the proper vertex-coloring produced by the greedy algorithm over the ordering in the list. Examples: greedy({"A" : ["B", "C"], "B" : ["A"], "C" : ["A"]},[“A”, “B”, “C”]) should return {“A” : 1, “B” : 2, "C" : 2} greedy({“A” : ["B"], "B" : [“A”, “C”],"C" : [“B”, “D”), “D" : ["C"]},[“A”, “D”, “B”, “C”]) should return {"A" : 1, “B” : 2, "C" : 3, "D" : 1}.

Answer 1

def greedy(g,l):
vertex = sorted(list(g.keys()), key=lambda x: len(g[x]), reverse=True) # sort in decending order
color = {}

for n in vertex:
Available_Colors= [True] * len(vertex)
for n_g in g[n]:
if n_g in color:
c = color[n_g]
Available_Colors[c] = False
for c, av in enumerate(Available_Colors):
if av:
color[n] = c
break

return color
g={'A':['B'],'B':['A','C'],'C':['B','D'],'D':['C']}
l=['A','B','C','D']
x=greedy(g,l)
print(x)


RESTART C:/Users/Sahil Chopra/AppData/Local/Programs/Python/Python37/jh.py >>> RESTART C:/Users/Sahil Chopra/AppData/Local/Programs/Python/Python37/jh.py {'A' 0, 'B': 1, 'C': 1} >>> RESTART: C:/Users/Sahil Chopra/AppData/Local/Programs/Python/Python37/jh.py 'B' 0, 'C': 1, 'A': 1, 'D': 0} >>>

jh.py - C/Users/Sahil Chopra/AppData/Local/Programs/Python/Python37/jh.py (3.7.0) File Edit Format Run Options Window Help def greedy (g, 1) vertex = sorted (list (g.keys ()), key=lambda x: len (g[x]), reverse=True) # so: color for nin vertex: Available Colors= [True] * len(vertex) for n g in g[n] if n_g in color c color[n g] Available Colors [C for c, av in enumerate (Available Colors): if av color [n] c = False break return color g=['A' : ['B', 'B':['A','C'],'c':['B','D'],'D':['C']} 1-'A', 'B','C','D'] x-greedy (g, 1) print (x)