Submission #74092521

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Source Code Expand

def count_even_0_to(n):
    if n < 0:
        return 0
    return n // 2 + 1

def black_prefix(a, b):
    # 0 <= x <= a, 0 <= y <= b にある黒点数
    if a < 0 or b < 0:
        return 0
    if a > b:
        a, b = b, a

    k = a // 2
    square = (k + 1) * (2 * k + 1)
    extra = (count_even_0_to(b) - count_even_0_to(a)) * (a + 1)
    return square + extra

def rect_nonneg(x1, x2, y1, y2):
    # 0 <= x1 <= x2, 0 <= y1 <= y2
    if x1 > x2 or y1 > y2:
        return 0
    return (
        black_prefix(x2, y2)
        - black_prefix(x1 - 1, y2)
        - black_prefix(x2, y1 - 1)
        + black_prefix(x1 - 1, y1 - 1)
    )

def count_axis(l, r):
    # 区間 [l,r] の整数のうち偶数の個数
    if l > r:
        return 0
    return r // 2 - (l - 1) // 2

def main():
    L, R, D, U = map(int, input().split())

    ans = 0

    # x<0, x=0, x>0 に分割し、y も同様に分割して数える
    # 負側は絶対値で正側へ写す

    # x>0, y>0
    ans += rect_nonneg(max(L, 1), max(R, 0), max(D, 1), max(U, 0))

    # x<0, y>0
    ans += rect_nonneg(max(-R, 1), max(-L, 0), max(D, 1), max(U, 0))

    # x>0, y<0
    ans += rect_nonneg(max(L, 1), max(R, 0), max(-U, 1), max(-D, 0))

    # x<0, y<0
    ans += rect_nonneg(max(-R, 1), max(-L, 0), max(-U, 1), max(-D, 0))

    # x=0
    if L <= 0 <= R:
        ans += count_axis(D, U)

    # y=0
    if D <= 0 <= U:
        ans += count_axis(L, R)

    # (0,0) を二重計上していれば 1 引く
    if L <= 0 <= R and D <= 0 <= U:
        ans -= 1

    print(ans)

if __name__ == "__main__":
    main()

Submission Info

Judge Result