20251123 baekjoon

code_study/Baekjoon/java/_15681.java

@@ -0,0 +1,54 @@
+import java.util.*;
+
+class Tree {
+    private int root;
+    private ArrayList<Integer>[] edges;
+    private int[] subTreeSizes;
+    private boolean[] visited;
+
+    public Tree(int root, int treeSize) {
+        this.root = root;
+        this.subTreeSizes = new int[treeSize+1];
+        this.visited = new boolean[treeSize+1];
+
+        this.edges = new ArrayList[treeSize + 1];
+        for(int i=0; i<=treeSize; i++) this.edges[i] = new ArrayList<>();
+    }
+
+    public void addEdge(int u, int v) {
+        this.edges[u].add(v);
+        this.edges[v].add(u);
+    }
+
+    public void printSubTreeSize(int node) {
+        System.out.println(this.subTreeSizes[node]);
+    }
+
+    public void countSubTreeSizes() {
+        this.dfs(root);
+    }
+
+    private void dfs(int current) {
+        this.visited[current] = true;
+        this.subTreeSizes[current] = 1;
+
+        for (int next : this.edges[current]) {
+            if(!this.visited[next]) {
+                dfs(next);
+                this.subTreeSizes[current] += this.subTreeSizes[next];
+            }
+        }
+    }
+}
+
+public class _15681 {
+    public static void main(String[] args) {
+        Scanner sc = new Scanner(System.in);
+        int N = sc.nextInt(), R = sc.nextInt(), Q = sc.nextInt();
+        Tree tree = new Tree(R, N);
+        for(int i=0; i<N-1; i++) tree.addEdge(sc.nextInt(), sc.nextInt());
+        tree.countSubTreeSizes();
+        for(int i=0; i<Q; i++) tree.printSubTreeSize(sc.nextInt());
+        sc.close();
+    }
+}