101. 孤岛的总面积

卡码网 101. 孤岛的总面积
代码随想录

from collections import deque
n, m = map(int, input().split())

matrix = []

for i in range(n):
    matrix.append(list(map(int, input().split())))

visited = [[False] * m for _ in range(n)]

directions = [[1,0],[-1,0],[0,-1],[0,1]]


def bfs(matrix, visited, x, y):
    area = 1
    que = deque([])
    que.append([x,y])
    flag = False
    while que:
        # 弹出一个点
        cur_x, cur_y = que.popleft()
        
        if cur_x == 0 or cur_x == len(matrix)-1 or cur_y ==0 or cur_y == len(matrix[0])-1:
            flag = True # 计算面积的同时判断是不是处理边界，如果是处于边界的话，就多返回一个true，只有不是边界的情况下才加到总面积上去。
        # 四个方向遍历（四个方向）
        for i, j in directions:
            next_x = cur_x + i
            next_y = cur_y + j
            if next_x < 0 or next_x >= len(matrix) or next_y < 0 or next_y >= len(matrix[0]):
                continue
            if not visited[next_x][next_y] and matrix[next_x][next_y] == 1:
                visited[next_x][next_y] = True
                que.append([next_x, next_y])
                area += 1
    return flag, area
res = 0

for i in range(n):
    for j in range(m):
        if matrix[i][j] == 1 and not visited[i][j]:
            visited[i][j] = True
            flag, area = bfs(matrix, visited, i, j)
            if not flag:
                res += area
            # if bfs(matrix, visited, i, j)  == 1:
            #     res += 1
print(res)

102. 沉没孤岛

卡码网 102. 沉没孤岛
代码随想录

from collections import deque
n, m = map(int, input().split())

matrix = []

for i in range(n):
    matrix.append(list(map(int, input().split())))

visited = [[False] * m for _ in range(n)]

directions = [[1,0],[-1,0],[0,-1],[0,1]]


def bfs(matrix, visited, x, y):
    area = 1
    que = deque([])
    que.append([x,y])
    flag = False
    back_up = deque([])
    while que:
        # 弹出一个点
        cur_x, cur_y = que.popleft()
        # 把遍历的所有点就记录下来，如果确定是一个孤岛，把这些左边置为0
        back_up.append([cur_x, cur_y])
        if cur_x == 0 or cur_x == len(matrix)-1 or cur_y ==0 or cur_y == len(matrix[0])-1:
            flag = True
        # 四个方向遍历（四个方向）
        for i, j in directions:
            next_x = cur_x + i
            next_y = cur_y + j
            if next_x < 0 or next_x >= len(matrix) or next_y < 0 or next_y >= len(matrix[0]):
                continue
            if not visited[next_x][next_y] and matrix[next_x][next_y] == 1:
                visited[next_x][next_y] = True
                que.append([next_x, next_y])
                area += 1
    if not flag:
        while back_up:
            cur_x, cur_y = back_up.popleft()
            matrix[cur_x][cur_y] = 0
            
    # return flag, area
res = 0

for i in range(n):
    for j in range(m):
        if matrix[i][j] == 1 and not visited[i][j]:
            visited[i][j] = True
            bfs(matrix, visited, i, j)
# print(res)
for i in range(len(matrix)):
    # print(" ".jion(map(str, matrix[i])))
    print(" ".join([str(item) for item in matrix[i]]).strip())

103. 水流问题

卡码网 103. 水流问题
代码随想录

from collections import deque
n, m = map(int, input().split())
 
matrix = []
 
for i in range(n):
    matrix.append(list(map(int, input().split())))
 
visited = [[False] * m for _ in range(n)]
 
directions = [[1,0],[-1,0],[0,-1],[0,1]]
 
first = set()
second = set()
 
def dfs(matrix, visited, x, y, node):
    if visited[x][y]:
        return
     
    node.add((x,y))
    visited[x][y] = True
     
    for i, j in directions:
        next_x = x + i
        next_y = y + j
        if (0 <= next_x < len(matrix) 
        and 0<= next_y < len(matrix[0]) 
        and matrix[next_x][next_y] >= matrix[x][y]):
            dfs(matrix, visited, next_x, next_y, node)
 
# 右/上
for i in range(len(matrix)):
    dfs(matrix, visited, i, 0, first)
for j in range(len(matrix[0])):
    dfs(matrix, visited, 0, j, first)
# print(first)
 
# visited需要重新初始化
visited = [[False] * m for _ in range(n)]
for i in range(len(matrix)):
    dfs(matrix, visited, i, len(matrix[0])-1, second)
for j in range(len(matrix[0])):
    dfs(matrix, visited, len(matrix)-1, j, second)
# print(second)
     
res = first & second
# print(res)
 
for x,y in res:
    print(f'{x} {y}')

104.建造最大岛屿

卡码网 104.建造最大岛屿
代码随想录

from collections import deque
n,m = map(int, input().split())

matrix = []

for i in range(n):
    matrix.append(list(map(int, input().split())))
# 记录遍历
visited = [[False]*m for _ in range(n)]
# 记录岛屿编号
marked = [[0]*m for i in range(n)]

directions = [[-1,0],[1,0],[0,-1],[0,1]]

def bfs(matrix, visited, x, y, marked, isoland_cnt):
    area = 1
    que = deque([])
    que.append([x,y])
    # 记录新的岛屿
    marked[x][y] = isoland_cnt
    while que:
        cur_x, cur_y = que.popleft()
        for i, j in directions:
            next_x = cur_x + i
            next_y = cur_y + j
            if next_x < 0 or next_x >= len(matrix) or next_y < 0 or next_y >= len(matrix[0]):
                continue
            if not visited[next_x][next_y] and matrix[next_x][next_y] == 1:
                visited[next_x][next_y] = True
                marked[next_x][next_y] = isoland_cnt
                que.append([next_x, next_y])
                area += 1
    return area

isoland_cnt = 1
area_dict = dict()
for i in range(n):
    for j in range(m):
        if matrix[i][j] == 1 and not visited[i][j]:
            visited[i][j] = True
            area = bfs(matrix, visited, i, j, marked, isoland_cnt)
            area_dict[isoland_cnt] = area
            isoland_cnt += 1

res = 0
# 开始填充
for i in range(n):
    for j in range(m):
        if marked[i][j] == 0:
            max_area = 1
            isoland_set = set()
            for x,y in directions:
                next_x = x + i
                next_y = y + j
                if (
                    0<= next_x < n and 
                    0 <= next_y < m and 
                    marked[next_x][next_y] != 0 and 
                    marked[next_x][next_y] not in isoland_set
                ):
                    max_area += area_dict[marked[next_x][next_y]]
                    isoland_set.add(marked[next_x][next_y])
            res = max(max_area, res)
if res == 0:
    print(n*m)
else:
    print(res)