Submission #626033

#	Time	Username	Problem	Language	Result	Execution time	Memory
626033		54skyxenon	Mecho (IOI09_mecho)	Cpython 3	19 / 100	1095 ms	25668 KiB

mecho

# https://oj.uz/problem/view/IOI09_mecho

from collections import deque
from math import ceil

n, s = map(int, input().split())

forest = []
for _ in range(n):
    forest.append(input())

start = None
end = None
hives = []

for i in range(n):
    for j in range(n):
        if forest[i][j] == 'M':
            start = (i, j)
        if forest[i][j] == 'D':
            end = (i, j)
        if forest[i][j] == 'H':
            hives.append((i, j))

def bs(lo, hi):
    def ok(mid):
        dist_hive = [[float('inf')] * n for _ in range(n)]
        dist_mecho = [[float('inf')] * n for _ in range(n)]
        dist_mecho[start[0]][start[1]] = mid

        hives_Q = deque()
        for i, j in hives:
            dist_hive[i][j] = 0
            hives_Q.append((i, j, 0))

        while hives_Q:
            r, c, depth = hives_Q.popleft()
            for nr, nc in [(r + 1, c), (r - 1, c), (r, c + 1), (r, c - 1)]:
                if 0 <= nr < n and 0 <= nc < n and forest[nr][nc] == 'G' and dist_hive[nr][nc] == float('inf'):
                    hives_Q.append((nr, nc, depth + 1))
                    dist_hive[nr][nc] = depth + 1

        mecho_Q = deque([(start[0], start[1], 0)])
        while mecho_Q:
            r, c, depth = mecho_Q.popleft()

            for nr, nc in [(r + 1, c), (r - 1, c), (r, c + 1), (r, c - 1)]:
                if 0 <= nr < n and 0 <= nc < n and forest[nr][nc] == 'G' and dist_mecho[nr][nc] == float('inf'):
                    mecho_Q.append((nr, nc, depth + 1))
                    dist_mecho[nr][nc] = mid + ceil((depth + 1) / s)

        # print('at mid =', mid)
        # print('dist_hive:')
        # print(*dist_hive, sep='\n')
        # print('dist_mecho:')
        # print(*dist_mecho, sep='\n')

        r, c = end
        for nr, nc in [(r + 1, c), (r - 1, c), (r, c + 1), (r, c - 1)]:
            if 0 <= nr < n and 0 <= nc < n and forest[nr][nc] == 'G' and dist_mecho[nr][nc] < dist_hive[nr][nc]:
                # print('mid =', mid, 'is good!')
                return True

        # print('mid =', mid, 'is bad!')
        return False

    if lo > hi:
        return -1

    mid = (lo + hi) // 2

    if not ok(mid):
        return bs(lo, mid - 1)
    elif mid < hi and ok(mid + 1):
        return bs(mid + 1, hi)
    else:
        return mid

print(bs(0, n ** 2))

• Subtask 1: 19 / 100