Ural 1250. Sea burial abstracts DFS from the problem

DFS first finds the sea and marks it out. Second, it marks the overseas DFS, and third, it finds the land.

The starting point of the second DFS is all the points around the graph, so that the four directions of DFS will mark the things not surrounded by the sea, and the rest will be surrounded by the sea.

It is difficult to read the questions and determine whether X and Y are abscissa or ordinate.

#include<iostream>#include<cstdio>#include<cstdlib>#include<cstring>#define MAXN 510using namespace std;int w,h,x,y;char map[MAXN][MAXN];bool vis[MAXN][MAXN];int move4[4][2]= {{0,1},{1,0},{-1,0},{0,-1}};int move8[8][2]= {{0,1},{0,-1},{-1,0},{1,0},{1,1},{-1,1},{1,-1},{-1,-1}};void dfssea(int a,int b){    if(map[a][b]=='1' ) return ;    if(map[a][b]!='.')  return ;    map[a][b]='1';    for(int i=0; i<8; i++)        dfssea(a+move8[i][0],b+move8[i][1]);}void dfsnotsea(int a,int b,char aim){    if(vis[a][b]==true)  return ;    if(map[a][b]=='1')  return ;    if(map[a][b]=='2')   return ;    map[a][b]=aim;    vis[a][b]=true;    for(int i=0; i<4; i++)        dfsnotsea(a+move4[i][0],b+move4[i][1],aim);}void dfs(int a,int b){    if(vis[a][b]||map[a][b]!='#')        return ;    vis[a][b]=true;    for(int i=0; i<4; i++)        dfs(a+move4[i][0],b+move4[i][1]);}int main(){    //freopen("in.txt","r",stdin);    scanf("%d%d%d%d",&w,&h,&x,&y);    getchar();    memset(map,'2',sizeof(map));    for(int i=1; i<=h; i++)    {        for(int j=1; j<=w; j++)            scanf("%c",&map[i][j]);        getchar();    }    memset(vis,false,sizeof(vis));    dfssea(y,x);    memset(vis,false,sizeof(vis));    for(int i=1; i<=w; i++)        dfsnotsea(1,i,'2');    for(int i=1; i<=w; i++)        dfsnotsea(h,i,'2');    for(int i=1; i<=h; i++)        dfsnotsea(i,1,'2');    for(int i=1; i<=h; i++)        dfsnotsea(i,w,'2');    memset(vis,false,sizeof(vis));    int ans=0;    for(int i=1; i<=h; i++)    {        for(int j=1; j<=w; j++)        {            if(map[i][j]=='#'&&vis[i][j]==false)            {                dfs(i,j);                ans++;            }        }    }    cout<<ans<<endl;    return 0;}