当前位置：首页 > article >正文

Leetcode 200 Number of Islands

article 2024/12/27 18:25:53

题意

给定一个二维矩阵，只含有0和1，1连接成片构成岛屿。求有多少个这样的岛屿

题目链接

https://leetcode.com/problems/number-of-islands/description/

思路

遍历二维矩阵，从遍历到之前没有visit到的1开始dfs, dfs是用来mark 已经遍历到的点为visited过。并且每次遇到没有visit过的1时计数。

题解

class Solution {
public:
    int m;
    int n;
    int numIslands(vector<vector<char>>& grid) {
        int res = 0;
        m = grid.size();
        n = grid[0].size();
        vector<vector<bool>> vis(m,vector<bool>(n,false));

        for(int i = 0; i < m; i++) {
            for(int j = 0; j < n; j++) {
                if(grid[i][j] == '1' && !vis[i][j]) {
                    dfs(grid, vis, i, j);
                    res += 1;
                }
            }
        }
        return res;
    }

    void dfs(vector<vector<char>>& grid, vector<vector<bool>>& vis,int x, int y) {
        vis[x][y] = true;
        int dk[] = {-1, 0, 1, 0, -1};
        for(int i = 0; i < 4; i++) {
            int nx = x + dk[i];
            int ny = y + dk[i+1];
            if(nx >= 0 && nx < m && ny >= 0 && ny < n && !vis[nx][ny] && grid[x][y] == '1') {
                dfs(grid, vis, nx, ny);
            }
        }
    }

};