200. 岛屿数量

class Solution {
public:
    int dir[4][2]={0,1,1,0,-1,0,0,-1};
    void bfs(vector>& grid,int x,int y,vector >&flag){
        queue >q;
        q.push({x,y});
        flag[x][y]=true;
        while(!q.empty()){
            pairp=q.front();
            q.pop();
            int xx=p.first;
            int yy=p.second;
            for(int i=0;i<4;i++){
               int xxx=xx+dir[i][0];
               int yyy=yy+dir[i][1];
                if(xxx<0||yyy<0||xxx>=grid.size()||yyy>=grid[0].size())continue;
               if(flag[xxx][yyy]==false&&grid[xxx][yyy]=='1'){
                   flag[xxx][yyy]=true;
                   q.push({xxx,yyy});
               }
            }
        }
    }
    int numIslands(vector>& grid) {
        int n=grid.size();
        int m=grid[0].size();
        int ans=0;
         vector >flag=vector >(n,vector(m,false));
        for(int i=0;i