問題の解決策を明らかにするのに非常に役立ちました。確率として 0.25 を使用すると (前述の )、誤解を招き、不正確になる可能性があります。確率 #dead_cases/#total_possible_moves を見ると、結果は異なります。
死ぬ/生き残ったケースを見つけるための次のコードを検討してください。
def winLoss_stat(N, steps):
newStats = [[[0, 0, 0] for i in range(N)] for j in range(N)]
if steps==0:
newStats = [[[1, 0, 0] for i in range(N)] for j in range(N)]
return newStats
oldStats = winLoss_stat(N, steps-1)
for i in range(N):
for j in range(N):
for d in [(0, 1), (0, -1), (1, 0), (-1, 0)]:
indX = i + d[0]
indY = j + d[1]
if indX >=0 and indX < N and indY >= 0 and indY<N:
newStats[i][j][0] += oldStats[indX][indY][0]
newStats[i][j][1] += oldStats[indX][indY][1]
newStats[i][j][2] += oldStats[indX][indY][2]
else:
newStats[i][j][1] += 1
if steps==1:
newStats[i][j][2] = 1
return newStats
(or equivalently, for one step (using dfs - recursive):
class winLoss:
def __init__(self, N):
self.win = 0
self.loss = 0
self.N = N
def winLoss(self, x, y, n):
if x < 0 or y < 0 or x >= self.N or y >= self.N:
self.loss += 1
return
if n == 0:
self.win += 1
return
self.winLoss(x - 1, y, n-1)
self.winLoss(x, y - 1, n-1)
self.winLoss(x+1, y, n-1)
self.winLoss(x, y+1, n-1)
wl = winLoss(n)
wl.winLoss(i, j, n)
for any i,j start point and n (size of square)
)
The winLoss_stat returns three values for starting point at each square i, j:
[numbers of survive cases, numbers of die cases before or at k steps, numbers of death exactly at step k]
The results are as the following for n=4 (4X4), steps=4:
0 1 2 3
0 [58, 24, 12] [93, 34, 18] [93, 34, 18] [58, 24, 12]
1 [93, 34, 18] [150, 46, 28] [150, 46, 28] [93, 34, 18]
2 [93, 34, 18] [150, 46, 28] [150, 46, 28] [93, 34, 18]
3 [58, 24, 12] [93, 34, 18] [93, 34, 18] [58, 24, 12]
This translates to the following probabilities for
1. death before or at k steps:
0 1 2 3
0 0.292683 0.267717 0.267717 0.292683
1 0.267717 0.234694 0.234694 0.267717
2 0.267717 0.234694 0.234694 0.267717
3 0.292683 0.267717 0.267717 0.292683
2. death exactly at k steps:
0 1 2 3
0 0.146341 0.141732 0.141732 0.146341
1 0.141732 0.142857 0.142857 0.141732
2 0.141732 0.142857 0.142857 0.141732
3 0.146341 0.141732 0.141732 0.146341
The results can be verified by looking at the numbers of win-loss from step 1 to 3 for n=3:
winLoss_stat(3, 1)
0 1 2
0 [2, 2, 1] [3, 1, 1] [2, 2, 1]
1 [3, 1, 1] [4, 0, 0] [3, 1, 1]
2 [2, 2, 1] [3, 1, 1] [2, 2, 1]
winLoss_stat(3, 2)
0 1 2
0 [6, 4, 2] [8, 5, 2] [6, 4, 2]
1 [8, 5, 2] [12, 4, 4] [8, 5, 2]
2 [6, 4, 2] [8, 5, 2] [6, 4, 2]
winLoss_stat(3, 3)
0 1 2
0 [16, 12, 4] [24, 13, 8] [16, 12, 4]
1 [24, 13, 8] [32, 20, 8] [24, 13, 8]
2 [16, 12, 4] [24, 13, 8] [16, 12, 4]