蓝桥杯2018 B组 第九题

#include <bits/stdc++.h>
#define M 1005
using namespace std;
 
int n;
char map1[M][M];
bool vis[M][M];
int dir[4][2] = {{1,0},{-1,0},{0,1},{0,-1}};
 
void dfs(int x,int y)
{
	vis[x][y] = 1;
	for(int i = 0; i < 4; i++)
	{
		int dx = x + dir[i][0];
		int dy = y + dir[i][1];
		if(dx >= 0 && dy >=0 && dx < n && dy < n && !vis[dx][dy] && map1[dx][dy] == '#')
			dfs(dx,dy);
	}
}
 
int main()
{
	cin>>n;
	int begin_count = 0,end_count = 0;
	for(int i = 0; i < n; i++)
		for(int j = 0; j < n; j++)
			cin>>map1[i][j];
 
	/*统计开始前岛屿个数*/
	for(int i = 0; i < n; i++)
		for(int j = 0; j < n; j++)
		{
			if(map1[i][j] == '#' && !vis[i][j])
				begin_count++,dfs(i,j);
		}
 
	/*淹没过程*/
	memset(vis,0,sizeof(vis));
	for(int i = 1; i < n-1; i++)
		for(int j = 1; j < n-1; j++)
		{
			if(map1[i][j] == '#'){
				if((map1[i+1][j]=='.'||map1[i-1][j]=='.'||map1[i][j+1]=='.'||map1[i][j-1]=='.'))
				map1[i][j] = '1';
			}
		}
 
	/*统计结束后岛屿个数*/
	memset(vis,0,sizeof(vis));
	for(int i = 0; i < n; i++)
		for(int j = 0; j < n; j++)
		{
			if(map1[i][j] == '#' && !vis[i][j])
				end_count++,dfs(i,j);
		}
 
	cout<<begin_count - end_count<<"\n";
	return 0;
}

比较简单的搜索题目，