Astar_algorithm.py

from queue import PriorityQueue
import random
import pygame
pygame.init()

WIDTH = 600
ROWS = 50

WIN = pygame.display.set_mode((WIDTH, WIDTH))
pygame.display.set_caption("A* path finding algorithm")

RED = (255, 0, 0)
GREEN = (0, 255, 0)
WHITE = (255, 255, 255)
BLACK = (0, 0, 0)
PURPLE = (128, 0, 128)
ORANGE = (255, 165 ,0)
GREY = (128, 128, 128)
TURQUOISE = (64, 224, 208)

"""
Represents each node point in the grid
"""
class Node:

    def __init__(self, row, col, width, total_rows):
        self.row = row
        self.col = col
        self.x = row * width
        self.y = col * width
        self.color = WHITE
        self.neighbours = []
        self.width = width
        self.total_rows = total_rows 

    def get_pos(self):
        return self.row, self.col

    def is_closed(self):
        return self.color == RED

    def is_open(self):
        return self.color == GREEN

    def is_barrier(self):
        return self.color == BLACK

    def is_start(self):
        return self.color == ORANGE

    def is_end(self):
        return self.color == TURQUOISE

    def reset(self):
        self.color = WHITE

    def make_start(self):
        self.color = ORANGE

    def make_end(self):
        self.color = TURQUOISE

    def make_closed(self):
        self.color = RED
    
    def make_open(self):
        self.color = GREEN

    def make_barrier(self):
        self.color = BLACK

    def make_path(self):
        self.color = PURPLE

    def draw(self, win):
        pygame.draw.rect(win, self.color, (self.x, self.y, self.width, self.width))

    def update_neighbours(self, grid):

        if self.row > 0 and not grid[self.row - 1][self.col].is_barrier():  #UP
            self.neighbours.append(grid[self.row - 1][self.col])

        if self.row < self.total_rows - 1 and not grid[self.row + 1][self.col].is_barrier():    #DOWN
            self.neighbours.append(grid[self.row + 1][self.col])

        if self.col < self.total_rows - 1 and not grid[self.row][self.col + 1].is_barrier():    #RIGHT
            self.neighbours.append(grid[self.row][self.col + 1])

        if self.col > 0 and not grid[self.row][self.col - 1].is_barrier():  #LEFT
            self.neighbours.append(grid[self.row][self.col - 1])

def h(p1, p2):
    x1, y1 = p1
    x2, y2 = p2
    return abs(x1 - x2) + abs(y1 - y2)

def reconstruct_path(came_from, current, draw):
    while current in came_from:
        current = came_from[current]
        current.make_path()
        draw()

def algorithm(draw, grid, start, end):
    count = 0
    open_set = PriorityQueue()
    open_set.put((0, count, start))
    came_from = {}
    g_score = {node: float("inf") for row in grid for node in row}
    g_score[start] = 0
    f_score = {node: float("inf") for row in grid for node in row}
    f_score[start] = h(start.get_pos(), end.get_pos())

    open_set_hash = {start}

    while not open_set.empty():
        for event in pygame.event.get():
            if event.type == pygame.QUIT:
                pygame.quit()
                return False

        current = open_set.get()[2]
        open_set_hash.remove(current)

        if current == end:
            reconstruct_path(came_from, end, draw)
            end.make_end()
            return True

        for neighbour in current.neighbours:
            temp_g_score = g_score[current] + 1

            if temp_g_score < g_score[neighbour]:
                came_from[neighbour] = current
                g_score[neighbour] = temp_g_score
                f_score[neighbour] = g_score[neighbour] + h(current.get_pos(), end.get_pos())
                if neighbour not in open_set_hash:
                    count += 1
                    open_set.put((f_score[neighbour], count, neighbour))
                    open_set_hash.add(neighbour)
                    neighbour.make_open()

        draw()

        if current != start:
            current.make_closed()
    
    return False

def make_grid(rows, width):
    grid = []
    gap = width // rows
    for i in range(rows):
        grid.append([])
        for j in range(rows):
            node = Node(i, j, gap, rows)
            grid[i].append(node)

    return grid

def draw_grid(win ,rows, width):
    gap = width // rows
    for i in range(rows):
        pygame.draw.line(win, GREY, (0, i * gap), (width, i * gap))
        for j in range(rows):
            pygame.draw.line(win, GREY, (j * gap, 0), (j * gap, width))

def draw(win, grid, rows, width):
    win.fill(WHITE)
            
    for row in grid:
        for node in row:
            node.draw(win)

    draw_grid(win, rows, width)
    pygame.display.update()

def get_clicked_pos(pos, rows, width):
    gap = width // rows
    y, x = pos
    
    row = y // gap
    col = x // gap

    return row, col

def main(win, rows, width):
    grid = make_grid(rows, width)
    start = None
    end = None

    # main loop
    run = True
    while run:
        draw(win, grid, rows, width)
        for event in pygame.event.get():
            if event.type == pygame.QUIT:
                run = False
                break

            if pygame.mouse.get_pressed()[0]:       #LEFT
                pos = pygame.mouse.get_pos()
                row, col = get_clicked_pos(pos, rows, width)
                node = grid[row][col]
                if not start and node != end:
                    start = node 
                    start.make_start()
                
                elif not end and node != start:
                    end = node
                    end.make_end()

                elif node != start and node != end:
                    node.make_barrier()

            elif pygame.mouse.get_pressed()[2]:     #RIGHT
                pos = pygame.mouse.get_pos()
                row, col = get_clicked_pos(pos, rows, width)
                node = grid[row][col]
                node.reset()
                if node == start:
                    start = None
                elif node == end:
                    end = None

            if event.type == pygame.KEYDOWN:
                # use the algorithm to find shortest path
                if event.key == pygame.K_SPACE and start and end:
                    for row in grid:
                        for node in row:
                            node.update_neighbours(grid)

                    algorithm(lambda: draw(win, grid, rows, width), grid, start, end)
                
                # reset the entire grid
                if event.key == pygame.K_r:
                    start = None
                    end = None
                    grid = make_grid(rows, width)

                # generate random maze
                if event.key == pygame.K_g:
                    start = None    # reset the start and end node points
                    end = None
                    grid = generate_random_maze(rows, width)

    pygame.quit()
  
def generate_random_maze(rows, width):
    grid = []

    gap = width // rows
    for i in range(rows):
        grid.append([])
        for j in range(rows):
            node = Node(i, j, gap, rows)
            grid[i].append(node)

    for i in range(rows):
        possible_rows = random.randrange(0, rows)
        for j in range(rows):
            if possible_rows:
                col = random.randrange(0, rows)
                node = grid[i][col]
                node.make_barrier()
                possible_rows -= 1

    return grid

main(WIN, ROWS, WIDTH)