深度优先搜索DFS2（c++）

题目练习

寻找边缘

#include <bits/stdc++.h>
using namespace std;
char a[110][110];
int n,m;

int dx[] = {0,1,0,-1};
int dy[] = {1,0,-1,0};
void dfs(int,int);
int main()
{
	int ttttt;
	cin>>ttttt;
	while(ttttt--)
	{
		cin>>n>>m;
		for(int i = 1;i<=n;i++)
		{
			for(int j = 1;j<=m;j++)
			{
				cin>>a[i][j];
			}
		}
		
		for(int i = 1;i<=n;i++)
			if(a[i][1]=='O') dfs(i,1);
		for(int i = 1;i<=n;i++)
			if(a[i][m]=='O') dfs(i,m);
		for(int i = 1;i<=m;i++)
			if(a[1][i]=='O') dfs(1,i);
		for(int i = 1;i<=m;i++)
			if(a[n][i]=='O') dfs(n,i);
		
		for(int i = 1;i<=n;i++)
		{
			for(int j = 1;j<=m;j++)
			{
				if(a[i][j]=='O') a[i][j] = 'X';
				if(a[i][j]=='1') a[i][j] = 'O';
				cout<<a[i][j];
			}
			cout<<endl;
		}
	}
	
	return 0;
}
void dfs(int x,int y)
{
	a[x][y] = '1';
	for(int i = 0;i<4;i++)
	{
		int tx = x+dx[i];
		int ty = y+dy[i];
		if(tx>1&&tx<=n&&ty>=1&&ty<=m&&a[tx][ty]=='O')
		{
			dfs(tx,ty);
		}
	}
	
	return;
}

卫星照片

#include <bits/stdc++.h>
using namespace std;
char a[110][110];
int n,m;

int dx[] = {0,1,0,-1};
int dy[] = {1,0,-1,0};
int c1,c2,cnt;
int sx,sy,ex,ey;
void dfs(int,int);
int main()
{
	cin>>n>>m;
	for(int i = 1;i<=n;i++)
	{
		for(int j = 1;j<=m;j++)
		{
			cin>>a[i][j];
		}
	}
	
	for(int i = 1;i<=n;i++)
	{
		for(int j = 1;j<=m;j++)
		{
			if(a[i][j]=='#')
			{
				cnt = 0;
				sx = i;
				ex = i;
				sy = j;
				ey = j;
				dfs(i,j);
				int mianji = (ex-sx+1)*(ey-sy+1);
				if(cnt==mianji) c1++;
				else c2++;
//				cout<<i<<" "<<j<<" "<<c1<<" "<<c2<<" "<<cnt<<endl;
			}
			
		}
	}
	cout<<c1<<endl<<c2;
	return 0;
}
void dfs(int x,int y)
{
	cnt++;
	a[x][y] = '.';
	sx = min(x,sx);
	ex = max(x,ex);
	sy = min(y,sy);
	ey = max(y,ey);
	for(int i = 0;i<4;i++)
	{
		int tx = x+dx[i];
		int ty = y+dy[i];
		if(tx>=1&&tx<=n&&ty>=1&&ty<=m&&a[tx][ty]=='#')
		{
			dfs(tx,ty);
		}
	}
	
	
	return;
}

城堡问题

#include <bits/stdc++.h>
using namespace std;
int a[110][110];
int n,m;
int cnt;
int ma;

int dx[] = {0,1,0,-1};
int dy[] = {1,0,-1,0};
//west1,north2,east4,south8

int dfs(int,int);
int main()
{
	cin>>n>>m;
	for(int i = 1;i<=n;i++)
	{
		for(int j = 1;j<=m;j++)
		{
			cin>>a[i][j];
			string ch;
			int t = a[i][j];
			while(t!=0)
			{
				ch = (char)(t%2+48)+ch;
				t /= 2;
			}
			a[i][j] = stoi(ch);
		}
	}
	for(int i = 1;i<=n;i++)
	{
		for(int j = 1;j<=m;j++)
		{
			if(a[i][j]>0)
			{
				cnt++;
				ma = max(ma,dfs(i,j));
			}
		}
	}
	cout<<cnt<<endl<<ma;
	return 0;
}
int dfs(int x,int y)
{
	a[x][y] = 0-cnt;
	int sum = 1;
	for(int i = 0;i<4;i++)
	{
		int tx = x+dx[i];
		int ty = y+dy[i];
		if(tx>=1&&tx<=n&&ty>=1&&ty<=m&&a[tx][ty]>0)
		{
			if(a[tx][ty]/100%10==0&&i==2) sum += dfs(tx,ty);
			if(a[tx][ty]/1000%10==0&&i==3) sum += dfs(tx,ty);
			if(a[tx][ty]/1%10==0&&i==0) sum += dfs(tx,ty);
			if(a[tx][ty]/10%10==0&&i==1) sum += dfs(tx,ty);
		}
	}
	return sum;
}