Contain Virus — LeetCode 749 Python Solution

class Solution:
    def containVirus(self, isInfected: List[List[int]]) -> int:
        def dfs(i, j):
            vis[i][j] = True
            areas[-1].append((i, j))
            for a, b in [[0, -1], [0, 1], [-1, 0], [1, 0]]:
                x, y = i + a, j + b
                if 0 <= x < m and 0 <= y < n:
                    if isInfected[x][y] == 1 and not vis[x][y]:
                        dfs(x, y)
                    elif isInfected[x][y] == 0:
                        c[-1] += 1
                        boundaries[-1].add((x, y))

        m, n = len(isInfected), len(isInfected[0])
        ans = 0
        while 1:
            vis = [[False] * n for _ in range(m)]
            areas = []
            c = []
            boundaries = []
            for i, row in enumerate(isInfected):
                for j, v in enumerate(row):
                    if v == 1 and not vis[i][j]:
                        areas.append([])
                        boundaries.append(set())
                        c.append(0)
                        dfs(i, j)
            if not areas:
                break
            idx = boundaries.index(max(boundaries, key=len))
            ans += c[idx]
            for k, area in enumerate(areas):
                if k == idx:
                    for i, j in area:
                        isInfected[i][j] = -1
                else:
                    for i, j in area:
                        for a, b in [[0, -1], [0, 1], [-1, 0], [1, 0]]:
                            x, y = i + a, j + b
                            if 0 <= x < m and 0 <= y < n and isInfected[x][y] == 0:
                                isInfected[x][y] = 1
        return ans