Hi, I am getting WA in this piece of code I have written. Can anyone please help me find my mistake. Thanks in advance.
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.util.HashMap;
import java.util.HashSet;
import java.util.StringTokenizer;
public class Main{
static BufferedReader br = new BufferedReader(new InputStreamReader(
System.in));
static PrintWriter out = new PrintWriter(System.out);
public static void main(String[] args) throws Exception {
int t = Integer.parseInt(br.readLine()), i, j, n;
HashMap<Integer, HashSet<Integer>> hm = new HashMap<Integer, HashSet<Integer>>();
StringTokenizer st;
for (i = 1; i <= t; i++) {
st = new StringTokenizer(br.readLine());
st.nextToken();
n = Integer.parseInt(st.nextToken());
boolean flag = false;
for (j = 0; j < n; j++) {
st = new StringTokenizer(br.readLine());
if (!flag) {
int key = Integer.parseInt(st.nextToken());
int value = Integer.parseInt(st.nextToken());
if (!hm.containsKey(key)) {
HashSet<Integer> hs = new HashSet<Integer>();
hs.add(value);
hm.put(key, hs);
} else {
HashSet<Integer> hs1 = new HashSet<Integer>(hm.get(key));
if (hs1.contains(value))
flag = true;
else
hs1.add(value);
hm.put(key, hs1);
}
}
}
if (flag)
out.println("Scenario #" + i + ": impossible");
else
out.println("Scenario #" + i + ": possible");
br.readLine();
}
out.flush();
}
}