1
#include<bits/stdc++.h>
2
using namespace std;
3
const int N=1e3+10;
4
int n,m,i,u,v,s,ans,a[N][N],vis[N],f[N];
5
void dfs(int t){
6
    int i;
7
    if(t==v){
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        s++;
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        for(i=1;i<=n;i++)if(vis[i])f[i]++;
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        return;
11
    }
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    for(i=1;i<=n;i++)if(a[t][i]&&!vis[i])vis[i]=1,dfs(i),vis[i]=0;
13
}
14
int main(){
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 cin>>n>>m;
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 for(i=1;i<=m;i++)cin>>u>>v,a[u][v]=a[v][u]=1;
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    cin>>u>>v;
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    dfs(u);
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    if(!s)return cout<<-1,0;
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    for(i=1;i<=n;i++)if(f[i]==s)ans++;
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    cout<<ans-1;
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}

1
#include<bits/stdc++.h>
2
using namespace std;
3
string a,b;
4
void _(string a,string b){
5
    if(a.size()){
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        char root=b[b.size()-1];
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        cout<<root;
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        int k=a.find(root);
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        _(a.substr(0,k),b.substr(0,k));
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        _(a.substr(k+1),b.substr(k,a.size()-k-1));
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    }
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}
13
int main(){
14
 cin>>a>>b;
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    _(a,b);
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}

1
#include<bits/stdc++.h>
2
using namespace std;
3
const int N=1e2,inf=INT_MAX;
4
int n,m,i,u,v,w,s,ans=-inf,a[N][N],vis[N];
5
void dfs(int t){
6
    int i;
7
    for(i=1;i<=n;i++)if(a[t][i]&&!vis[i])vis[i]=1,s+=a[t][i],dfs(i),s-=a[t][i];
8
    ans=max(ans,s);vis[t]=0;
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}
10
int main(){
11
 cin>>n>>m;
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 for(i=1;i<=m;i++)cin>>u>>v>>w,a[u][v]=a[v][u]=w;
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    for(i=1;i<=n;i++)memset(vis,0,sizeof vis),vis[i]=1,dfs(i);
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    cout<<ans;
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}

1
##    ##    #.    .#
2
#.    .#    ##    ##

1
#include<bits/stdc++.h>
2
using namespace std;
3
const int N=1e3+10;
4
int n,m,i,j,ans;
5
char a[N][N];
6
bool check(int x,int y){
7
 int s=0;
8
 if(a[x][y]=='#')s++;
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 if(a[x+1][y]=='#')s++;
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 if(a[x][y+1]=='#')s++;
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 if(a[x+1][y+1]=='#')s++;
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 return s==3;
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}
14
int main(){
15
 cin>>n>>m;
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 for(i=1;i<=n;i++)for(j=1;j<=m;j++)cin>>a[i][j];
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 for(i=1;i<n;i++)for(j=1;j<m;j++)if(check(i,j))return cout<<"Bad placement.",0;
18
 for(i=1;i<=n;i++)for(j=1;j<=m;j++)if(a[i][j]=='#'&&a[i-1][j]!='#'&&a[i][j-1]!='#')ans++;
19
 cout<<"There are "<<ans<<" ships.";
20
}