05.森林火灾模型

"""
森林火灾模型:
"森林"最初只是一个空的N×N网格。每个周期在网格上随机选择一个格点。
如果该格点为空，那么就以概率 g 在那里种上一棵树。
如果该格点上已经有树，那么闪电会以概率（1-g）击中该格点。
如果该格点有一棵树，那么树会着火，火势会蔓延到所有连接到该格点的有树的格点。
"""
import numpy as np
from random import randint, uniform
from collections import Counter
import matplotlib.pyplot as plt


def forest_fire_model(grid, g):
    i, j = randint(0, len(grid) - 1), randint(0, len(grid) - 1)
    p = uniform(0, 1)

    if not grid[i][j] and p <= g:
        grid[i][j] = 1
    if grid[i][j] and p <= 1 - g:
        grid[i][j] = 0
        if j >= 1:
            grid[i][j - 1] = 0
        if i >= 1:
            grid[i - 1][j] = 0
        if i <= len(grid) - 2:
            grid[i + 1][j] = 0
        if j <= len(grid) - 2:
            grid[i][j + 1] = 0

    return grid


if __name__ == "__main__":
    grid = np.zeros((10, 10), dtype=np.int)
    # tree_num = []

    for i in range(100000):
        grid = forest_fire_model(grid, 0.6)
        # 统计数组中某个元素的个数的两种方法
        # tree = Counter(grid.flat)[1]
        # tree = np.sum(grid == 1)
        # tree_num.append(tree)

    plt.imshow(grid)
    plt.show()