2020-09-28

1.https://vjudge.net/contest/397650#problem/B

#include <bits/stdc++.h>
using namespace std;
const int Max=21; 
char mapp[Max][Max];
int vis[Max][Max]; 
int dir[4][2]={{-1,0},{0,1},{1,0},{0,-1}};
int w,h,sx,sy,step=0;
void dfs(int x,int y){
	int nx,ny;
	step++;
	vis[x][y]=1;
	for(int i=0;i<4;i++){
		nx=x+dir[i][0];
		ny=y+dir[i][1];
		if(mapp[nx][ny]=='.'&&!vis[nx][ny]&&nx>=0&&nx<h&&ny>=0&&ny<w){
			//vis[nx][ny]=1;
			dfs(nx,ny);
			//vis[nx][ny]=0;
		}
	}
}
int main(){
	cin>>w>>h;
	for(int i=0;i<h;i++)	
		for(int j=0;j<w;j++){
			cin>>mapp[i][j];
			if(mapp[i][j]=='@'){
				sx=i;
				sy=j;
			}
		}
	//vis[sx][sy]=1;
	dfs(sx,sy);	
	cout<<step<<endl;
	return 0;
}

2.https://vjudge.net/contest/397650#problem/C

#include <bits/stdc++.h>
using namespace std;
int n;
bool judge1(int x){
	for(int i=2;i*i<=x;i++){
		if(x%i==0)
			return false; 
	}
	return true;
}
bool judge2(int x){
	if(x<100){
		int a=x%10;
		int b=x/10;
		if(a==b)
			return true;
	}
	else{
		int a=x%10;
		int b=(x/10)/10;
		if(a==b)
			return true;
	}
	return false;
}
int main(){
	int ans=0;
	cin>>n;
	for(int i=11;i<=n;i++){
		if(judge1(i)&&judge2(i))
			ans++;
	}
	cout<<ans<<endl;
	return 0;
}