#Leetcode# 200. Number of Islands
https://leetcode.com/problems/number-of-islands/
Given a 2d grid map of '1'
s (land) and '0'
s (water), count the number of islands. An island is surrounded by water and is formed by connecting adjacent lands horizontally or vertically. You may assume all four edges of the grid are all surrounded by water.
Example 1:
Input: 11110 11010 11000 00000 Output: 1
Example 2:
Input: 11000 11000 00100 00011 Output: 3
代码:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 | class Solution { public : int numIslands(vector<vector< char >>& grid) { if (grid.empty() || grid[0].empty()) return 0; int n = grid.size(), m = grid[0].size(); int ans = 0; vector<vector< bool > > flag(n, vector< bool > (m, false )); for ( int i = 0; i < n; i ++) { for ( int j = 0; j < m; j ++) { if (grid[i][j] == '1' && !flag[i][j]) { dfs(grid, flag, i, j); ans ++; } } } return ans; } void dfs(vector<vector< char > > &grid, vector<vector< bool > > &flag, int x, int y) { if (x < 0 || x >= grid.size()) return ; if (y < 0 || y >= grid[0].size()) return ; if (grid[x][y] != '1' || flag[x][y]) return ; flag[x][y] = true ; dfs(grid, flag, x - 1, y); dfs(grid, flag, x + 1, y); dfs(grid, flag, x, y - 1); dfs(grid, flag, x, y + 1); } }; |
求连续区域的个数 flag 记录是不是被访问过 对于每一个值是 1 的上下左右 dfs 把和它连着的 1 都标记住 搜索完 ans 加一 dfs 还是要好好学的哇
【推荐】编程新体验,更懂你的AI,立即体验豆包MarsCode编程助手
【推荐】凌霞软件回馈社区,博客园 & 1Panel & Halo 联合会员上线
【推荐】抖音旗下AI助手豆包,你的智能百科全书,全免费不限次数
【推荐】轻量又高性能的 SSH 工具 IShell:AI 加持,快人一步