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BOJ_2843.java
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BOJ_2843.java
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import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.HashSet;
import java.util.StringTokenizer;
class Query {
int op, x;
public Query(int op, int x) {
this.op = op;
this.x = x;
}
}
public class Main {
private static final BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
private static final int OP_ERASE = 2;
private static final int OP_QUERY = 1;
private static final int UF_ROOT = -1;
private static final int UF_CYCLE = -2;
int[] parents;
boolean[] cycle;
public static void main(String[] args) throws Exception {
new Main().solution();
}
private boolean isCycle(int a) {
return parents[find(a)] == UF_CYCLE;
}
private int find(int a) {
if (parents[a] < 0)
return a;
return parents[a] = find(parents[a]);
}
private void union(int a, int b) {
a = find(a);
b = find(b);
if (a==b) {
parents[b] = UF_CYCLE;
return;
}
parents[a] = b;
}
public void solution() throws Exception {
int n = Integer.parseInt(br.readLine());
parents = new int[n+1];
cycle = new boolean[n+1];
Arrays.fill(parents, UF_ROOT);
int[] edge = new int[n+1];
StringTokenizer st = new StringTokenizer(br.readLine());
for (int i = 1; i <= n; i++) {
edge[i] = Integer.parseInt(st.nextToken());
}
int q = Integer.parseInt(br.readLine());
Query[] queries = new Query[q];
HashSet<Integer> except = new HashSet<>();
for (int i = 0; i < q; i++) {
st = new StringTokenizer(br.readLine());
int op = Integer.parseInt(st.nextToken());
int x = Integer.parseInt(st.nextToken());
queries[i] = new Query(op, x);
if (op == OP_ERASE)
except.add(x);
}
for (int i = 1; i <= n; i++) {
if (except.contains(i) || edge[i] == 0) continue;
union(i, edge[i]);
}
ArrayList<Integer> answer = new ArrayList<>();
for (int i = q-1; i >= 0; i--) {
if (queries[i].op == OP_QUERY) {
answer.add(isCycle(queries[i].x) ? UF_CYCLE : find(queries[i].x));
} else {
int a = queries[i].x;
int b = edge[a];
if (b!=0)
union(a, b);
}
}
StringBuilder sb = new StringBuilder();
for (int i = answer.size()-1; i >= 0; i--) {
sb.append(answer.get(i) == UF_CYCLE ? "CIKLUS" : answer.get(i)).append('\n');
}
System.out.print(sb);
}
}