LeetCode 0200 - Number of Islands

Reck Zhang

发布于 2021-08-11 14:56:18

3250

发布于 2021-08-11 14:56:18

文章被收录于专栏：Reck Zhang Reck ZhangReck Zhang

Number of Islands

Desicription

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

Solution

class Solution {
private:
    int n;
    int m;
    int dir[4][2] = {1, 0, -1, 0, 0, -1, 0, 1};
    void dfs(int x, int y, vector<vector<char>>& grid) {
        if(grid[x][y] == '1')
            grid[x][y] = '0';
        for(int i = 0; i < 4; i++) {
            int dx = x + dir[i][0];
            int dy = y + dir[i][1];
            if(dx < 0 || dx == n || dy < 0 || dy >= m || grid[dx][dy] == '0')
                continue;
            dfs(dx, dy, grid);
        }
    }
public:
    int numIslands(vector<vector<char>>& grid) {
        if(grid.size() == 0)
            return 0;
        n = grid.size();
        m = grid[0].size();
        int res = 0;
        for(int i = 0; i < n; i++) {
            for(int j = 0; j < m; j++) {
                if(grid[i][j] == '1') {
                    res++;
                    dfs(i, j, grid);
                }
            }
        }
        return res;
    }
};

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原始发表：2018-06-12，如有侵权请联系 cloudcommunity@tencent.com 删除

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