leetcode 200. 岛屿数量

其实很简单，用dfs很快解出

class Solution {
public:
    int ans;
    void dfs(vector<vector<char>>& grid,vector<vector<int>>& visit,int i,int j,int n,int m){
        if(i<0||i>=n||j<0||j>=m||grid[i][j]=='0') return;
        grid[i][j]='0';
        dfs(grid,visit,i+1,j,n,m);
        dfs(grid,visit,i-1,j,n,m);
        dfs(grid,visit,i,j-1,n,m);
        dfs(grid,visit,i,j+1,n,m);
    }
    int numIslands(vector<vector<char>>& grid) {
        if(!grid.size()) return ans;
        int n=grid.size(),m=grid[0].size();
        if(!n||!m) return ans;
        vector<vector<int>> visit(n+1,vector<int>(m+1,0));
        for(int i=0;i<n;i++)
            for(int j=0;j<m;j++)
                if(!visit[i][j]&&grid[i][j]=='1'){
                    visit[i][j]==1;
                    ++ans;
                    dfs(grid,visit,i,j,n,m);}
        return ans;
    }
};

结果：