Leetcode 刷题笔记1 图论part02

卡码网 99 岛屿数量

深搜版：

direction = [[0, 1], [1, 0], [0, -1], [-1, 0]]
 
def main():
    n, m  = map(int, input().split())
    grid = []
    res = 0
    for i in range(n):
        grid.append(list(map(int, input().split())))
    visited = [[False] * m for _ in range(n)]
    for i in range(n):
        for j in range(m):
            if grid[i][j] == 1 and not visited[i][j]:
                res += 1
                dfs(grid, visited, i, j)
    print(res)
 
def dfs(grid, visited, i, j):
    if visited[i][j] or grid[i][j] == 0:
        return
    visited[i][j] = True
    for x, y in direction:
        next_x = i + x 
        next_y = j + y 
        if next_x < 0 or next_x >= len(grid) or next_y < 0 or next_y >= len(grid[0]):
            continue
        dfs(grid, visited, next_x, next_y)
 
if __name__ == '__main__':
    main()

 广搜版：

from collections import deque
directions = [[0, 1], [1, 0], [0, -1], [-1, 0]]
def main():
    n, m = map(int, input().split())
    grid = []
    for i in range(n):
        grid.append(list(map(int, input().split())))
    visited = [[False] * m for _ in range(n)]
    res = 0
    for i in range(n):
        for j in range(m):
            if not visited[i][j] and grid[i][j] == 1:
                res += 1
                bfs(grid, visited, i, j)
    print(res)
 
def bfs(grid, visited, x, y):
    que = deque([])
    que.append([x, y])
    visited[x][y] = True
    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(grid) or next_y < 0 or next_y >= len(grid[0]):
                continue
            if not visited[next_x][next_y] and grid[next_x][next_y] == 1:
                visited[next_x][next_y] = True
                que.append([next_x, next_y])
     
 
if __name__ == '__main__':
    main()

卡码网 100 岛屿的最大面积

学习全局变量的使用

from collections import deque
directions = [[0, 1], [1, 0], [0, -1], [-1, 0]]
count = 0

def bfs(grid, visited, x, y):
    global count
    que = deque()
    que.append([x, y])
    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(grid) or next_y < 0 or next_y >= len(grid[0]):
                continue
            if grid[next_x][next_y] == 1 and not visited[next_x][next_y]:
                count += 1
                visited[next_x][next_y] = True
                que.append([next_x, next_y])

def main():
    global count
    n, m = map(int, input().split())
    grid = []
    for _ in range(n):
        grid.append(list(map(int, input().split())))
    visited = [[False] * m for _ in range(n)]
    res = 0
    for i in range(n):
        for j in range(m):
            if grid[i][j] == 1 and not visited[i][j]:
                count = 1
                visited[i][j]  = True
                bfs(grid, visited, i, j)
                res = max(count, res)
    print(res)

if __name__ == '__main__':
    main()