def find_blank_square(self, state):
        """Return the index of the blank square in a given state"""
        for row in len(state):
            for column in len(row):
                if state[row][column] == 0:
                    index_blank_square = (row, column)
        return index_blank_square

    def goal_test(self, state):
        """Given a state, return True if state is a goal state or False, otherwise"""
        for row in len(state):
            for column in len(row):
                if state[row][col] != self.goal[row][column]:
                    return False
        return True

    def h(self, state):
        """Return the heuristic value for a given state. Heuristic function used is 
        h(n) = number of misplaced tiles."""
        num_misplaced_tiles = 0
        for row in len(state):
            for column in len(row):
                if state[row][col] != self.goal[row][column]:
                    num_misplaced_tiles += 1
        return num_misplaced_tiles