hamiltonian_cycle.py

class Graph():
    def __init__(self, vertices):
        self.graph = [[0 for column in range(vertices)]
                      for row in range(vertices)]
        self.V = vertices

    def isSafe(self, v, pos, path):
        if self.graph[path[pos-1]][v] == 0:
            return False
        for vertex in path:
            if vertex == v:
                return False
        return True

    def hamCycleUtil(self, path, pos):

        if pos == self.V:
            if self.graph[path[pos-1]][path[0]] == 1:
                return True
            else:
                return False
        for v in range(1, self.V):

            if self.isSafe(v, pos, path) == True:

                path[pos] = v

                if self.hamCycleUtil(path, pos+1) == True:
                    return True
                path[pos] = -1

        return False

    def hamCycle(self):
        path = [-1] * self.V
        path[0] = 0

        if self.hamCycleUtil(path, 1) == False:
            print("Solution does not exist\n")
            return False

        self.printSolution(path)
        return True

    def printSolution(self, path):
        print("Solution Exists: Following",
              "is one Hamiltonian Cycle")
        for vertex in path:
            print(vertex, end=" ")
        print(path[0], "\n")


g1 = Graph(5)
g1.graph = [[0, 1, 0, 1, 0], [1, 0, 1, 1, 1],
            [0, 1, 0, 0, 1, ], [1, 1, 0, 0, 1],
            [0, 1, 1, 1, 0], ]

g1.hamCycle()

# g2 = Graph(5)
# g2.graph = [[0, 1, 0, 1, 0], [1, 0, 1, 1, 1],
#             [0, 1, 0, 0, 1, ], [1, 1, 0, 0, 0],
#             [0, 1, 1, 0, 0], ]

# g2.hamCycle()