usaco 4.4.3 Frame Up

/*
ID: daniel.20
LANG: JAVA
TASK: frameup
*/
import java.util.*;
import java.io.*;
import java.math.BigInteger;

class problem22{
StringBuilder sb = new StringBuilder();
long start = System.currentTimeMillis();
int H,W;
char[][] arr;
int left[] = new int[26];
int right[] = new int[26];
int top[] = new int[26];
int bottom[] = new int[26];
boolean vis[] = new boolean[26];
ArrayList<String> l = new ArrayList<String>();
int[][] relation = new int[26][26];
int count[] = new int[26];
char[] path = new char[26];
int total = 0;
void solver() throws IOException{
BufferedReader reader = new BufferedReader(new FileReader("frameup.in"));
Arrays.fill(left, 999);
Arrays.fill(right, -1);
Arrays.fill(top, 999);
Arrays.fill(bottom, -1);
StringTokenizer st = new StringTokenizer(reader.readLine());
H=Integer.valueOf(st.nextToken());
W=Integer.valueOf(st.nextToken());
arr = new char[H][W];
for(int i=0;i<H;i++){
String tmp = reader.readLine();
for(int j=0;j<W;j++){
arr[i][j]=tmp.charAt(j);
if(arr[i][j]=='.') continue;
int temp = arr[i][j]-'A';
left[temp]=left[temp]<j?left[temp]:j;
right[temp]=right[temp]>j?right[temp]:j;
top[temp]=top[temp]<i?top[temp]:i;
bottom[temp]=bottom[temp]>i?bottom[temp]:i;
}
}
for(int i=0;i<26;i++){
if(left[i]==999) continue;
int cnt=0;
total++;
for(int k1=left[i];k1<=right[i];k1++){
if(arr[top[i]][k1]-'A'!=i){
relation[i][arr[top[i]][k1]-'A'] = -1;
cnt++;
}
if(arr[bottom[i]][k1]-'A'!=i){
relation[i][arr[bottom[i]][k1]-'A'] = -1;
cnt++;
}
}
for(int k2=top[i];k2<=bottom[i];k2++){
if(arr[k2][left[i]]-'A'!=i){
relation[i][arr[k2][left[i]]-'A'] = -1;
cnt++;
}
if(arr[k2][right[i]]-'A'!=i){
relation[i][arr[k2][right[i]]-'A'] = -1;
cnt++;
}
}
count[i]= cnt;
}
for(int i=0;i<26;i++){
if(left[i]==999||!ok(i)) continue;
path[0]=(char)(i+'A');
dfs(i,1);
path[0]=0;
}
Collections.sort(l);
for(String x:l){
sb.append(x).append("\n");
}
//System.out.print(sb.toString());
PrintWriter pw = new PrintWriter(new BufferedWriter(new FileWriter("frameup.out")));
pw.print(sb.toString());
pw.close();
System.out.println("$:"+(System.currentTimeMillis()-start));
System.exit(0);
}
boolean ok(int n){
for(int i=0;i<26;i++){
if(left[i]==999) continue;
if(!vis[i]&&relation[i]
==-1) return false; //i should be before n, so when we about to place n, vis[i] should be true
}
return true;
}
void dfs(int c, int level){
if(level==total){
String s = new String(path,0,level);
l.add(s);
return;
}
vis[c]=true;
for(int i=0;i<26;i++){
if(left[i]==999||vis[i]) continue;
if(ok(i)){
path[level]=(char)(i+'A');
dfs(i,level+1);
path[level]=0;
}
}
vis[c]=false;
}
}
public class frameup {
public static void main(String[] args) throws Exception {
problem22 p = new problem22();
p.solver();
}
}