D - Escape Route https://atcoder.jp/contests/abc405/tasks/abc405_d

abc405_d.py

from collections import deque

H, W = map(int, input().split())
S = [list(input()) for _ in range(H)]
ans = [row[:] for row in S]

dist = [[float("inf")] * W for _ in range(H)]
dq = deque()
for y in range(H):
    for x in range(W):
        if S[y][x] == "E":
            dq.append((x, y))
            dist[y][x] = 0
            
dirs = [(0, 1, "^"), (1, 0, "<"), (0, -1, "v"), (-1, 0, ">")]
while dq:
    x, y = dq.popleft()
    for dx, dy, arrow in dirs:
        nx, ny = x + dx, y + dy
        if nx < 0 or nx >= W or ny < 0 or ny >= H:
            continue
        if S[ny][nx] != ".":
            continue
        if dist[ny][nx] != float('inf'):
            continue
        dist[ny][nx] = dist[y][x] + 1
        ans[ny][nx] = arrow
        dq.append((nx, ny))

for row in ans:
    print("".join(row))