Submission #1674562

---

Source Code Expand

import numpy as np


def combi(l, r):
    if l == 0 or l == r:
        return 1
    answer = 1
    for i in range(l - r + 1, l + 1):
        answer *= i
    for i in range(1, r + 1):
        answer //= i
    return answer


def power(a, b):
    answer = 1
    for i in range(b):
        answer *= a
    return answer


N, D = [int(x) for x in input().split(' ')]
X, Y = [int(x) for x in input().split(' ')]

if abs(X) % D != 0 or abs(Y) % D != 0:
    print(0.0)
else:
    X = abs(X) // D
    Y = abs(Y) // D
    stack = [(0, 0, N)]
    prob = 0
    while len(stack) != 0:
        x, y, step = stack.pop(0)
        if step < abs(X - x) + abs(Y - y):
            pass
        elif step == abs(X - x) + abs(Y - y):
            prob += combi(step, abs(X - x)) * combi(step - abs(X - x), abs(Y - y))
        else:
            stack = [(x + 1, y, step - 1), (x - 1, y, step - 1), (x, y + 1, step - 1), (x, y - 1, step - 1)] + stack

    print(np.exp(np.log(prob) + N * np.log(0.25)))

Submission Info

Judge Result