PriorityQueue.py

# Author : Junth Basnet

import numpy as np


class PriorityQueue(object):
    def __init__(self):
        self.queue = []
        self.goal_state = np.array([
            1, 2, 3,
            8, 0, 4,
            7, 6, 5
        ])

    def h(self, start, goal):
        """ Calculates the different between the given puzzles """
        start = np.array(start).reshape((3, 3))
        goal = np.array(goal).reshape((3, 3))

        temp = 0
        for i in range(0, 3):
            for j in range(0, 3):
                if start[i][j] != goal[i][j] and start[i][j] != 0:
                    temp += 1
        return temp

    def __str__(self):
        return ' '.join([str(i) for i in self.queue])

    # for checking if the queue is empty
    def is_empty(self):
        return len(self.queue) == []

    # for inserting an element in the queue
    def push(self, sent_state, check_value=True, value=0):
        if check_value:
            manhattan_distance = self.h(sent_state.state, self.goal_state)
            self.queue.append([manhattan_distance, sent_state])
        else:
            self.queue.append(value)

    # for popping an element based on Priority
    def pop(self, value=True):
        try:
            minimum = 0
            for i in range(len(self.queue)):
                if value:
                    if self.queue[i][0] < self.queue[minimum][0]:
                        minimum = i
                else:
                    if self.queue[i] < self.queue[minimum]:
                        minimum = i
            item = self.queue[minimum]
            del self.queue[minimum]
            return item
        except IndexError:
            print()
            exit()