【代码随想录训练营】【Day 65】【图论-2】| 卡码 99

【代码随想录训练营】【Day 65】【图论-2】| 卡码 99

需强化知识点

• 深度搜索和广度搜索

题目

99. 岛屿数量

思想：遍历到为1的节点，再搜索标记，每遇到新的陆地节点，增加计数

• 深度搜索
• 广度搜索：此处用 [] 作为待遍历队列也可，que（append，popleft）

import collectionsdef dfs(grid, visited, x, y):dirs = [[0, 1], [0, -1], [1, 0], [-1, 0]]for add_x, add_y in dirs:next_x = x + add_xnext_y = y + add_yif next_x < 0 or next_x >= len(grid) or next_y < 0 or next_y >= len(grid[0]):continueif not visited[next_x][next_y] and grid[next_x][next_y]:visited[next_x][next_y] = Truedfs(grid, visited, next_x, next_y)def bfs(grid, visited, x, y):dirs = [[0, 1], [0, -1], [1, 0], [-1, 0]]que = collections.deque()# que = []que.append([x, y])visited[x][y] = Truewhile que:# cur = que.pop()cur = que.popleft()cur_x = cur[0]cur_y = cur[1]for add_x, add_y in dirs:next_x = cur_x + add_xnext_y = cur_y + add_yif next_x < 0 or next_x >= len(grid) or next_y < 0 or next_y >= len(grid[0]):continueif not visited[next_x][next_y] and grid[next_x][next_y]:que.append([next_x, next_y])visited[next_x][next_y] = Truetmp = list(map(int, input().split()))
m, n = tmp[0], tmp[1]grid = [[0]*n for _ in range(m)]
visited = [[False]*n for _ in range(m)]
for i in range(m):tmp = list(map(int, input().split()))for j in range(n):grid[i][j] = tmp[j]result = 0
for i in range(m):for j in range(n):if not visited[i][j] and grid[i][j]:visited[i][j] = Trueresult += 1bfs(grid, visited, i, j)print(result)