[Link] https://www.acmicpc.net/problem/3584
Common Dynamic Progrmming Solution
Common Dynamic Progrmming Solution
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import java.util.*;
import java.io.*;
public class Main {
static BufferedReader br;
static StringBuilder sb = new StringBuilder();
static int[] containsV1;
static int[] containsV2;
public static void main(String[] args) throws IOException {
br = new BufferedReader(new InputStreamReader(System.in));
int t = toi(br.readLine());
Node[] nodes;
int[] arr;
for(int iter = 0; iter < t; iter++) {
int n = toi(br.readLine());
nodes = new Node[n];
for(int i = 0; i < n; i++) nodes[i] = new Node(i);
containsV1 = new int[n];
containsV2 = new int[n];
Arrays.fill(containsV1, -1);
Arrays.fill(containsV2, -1);
for(int i = 0; i < n - 1; i++) {
arr = getArr();
int a = arr[0] - 1, b = arr[1] - 1;
nodes[a].list.add(nodes[b]);
nodes[b].parent = a;
}
int rootIdx = 0;
for(int i = 0; i < n; i++) {
if(nodes[i].parent == -1) {
rootIdx = i;
break;
}
}
arr = getArr();
sb.append(getCommonParent(nodes[rootIdx], arr[0] - 1, arr[1] - 1) + 1).append("\n");
}
print(sb);
}
static int getCommonParent(Node node, int a, int b) {
int store = 0;
while(true) {
boolean next = false;
for(Node child: node.list) {
if(contains1(child, a) == 1 && contains2(child, b) == 1) {
node = child;
next = true;
}
}
if(!next) break;
} return node.idx;
}
static int contains1(Node node, int idx) {
if(containsV1[idx] != -1) return containsV1[node.idx];
if(node.idx == idx) return containsV1[node.idx] = 1;
for(Node e : node.list) {
if(contains1(e, idx) == 1) return containsV1[node.idx] = 1;
}
return containsV1[node.idx] = 0;
}
static int contains2(Node node, int idx) {
if(containsV2[idx] != -1) return containsV2[node.idx];
if(node.idx == idx) return containsV2[node.idx] = 1;
for(Node e : node.list) {
if(contains2(e, idx) == 1) return containsV2[node.idx] = 1;
}
return containsV2[node.idx] = 0;
}
static class Node {
int idx;
int parent = -1;
ArrayList<Node> list = new ArrayList<>();
public Node(int idx) { this.idx = idx; }
}
static int toi(String s) { return Integer.parseInt(s); }
static long tol(String s) { return Long.parseLong(s); }
static String[] getLine() throws IOException { return br.readLine().split(" "); }
static int[] getArr() throws IOException { return Arrays.stream(br.readLine().split(" ")).mapToInt(Integer::parseInt).toArray(); }
static <T> void print(T s) { System.out.print(s); }
static <T> void println(T s) { System.out.println(s); }
}