[트리] 1870063 윤혜원

12_트리/필수/BOJ_15681.cpp

@@ -0,0 +1,59 @@
+#include <iostream>
+#include <vector>
+#include <map>
+
+using namespace std;
+
+map<int, vector<int>> tree;
+vector<int> edge_v[100001];
+int nodeSize[100001];
+
+void makeTree(int current, int parent) {
+	for (int node : edge_v[current]) {
+		if (node != parent) {
+			tree[current].push_back(node);
+			makeTree(node, current);
+		}
+	}
+	return;
+}
+
+void countNode(int node) {
+	nodeSize[node] = 1;
+
+	for (int child : tree[node]) {
+		countNode(child);
+		nodeSize[node] += nodeSize[child];
+	}
+	return;		
+}
+
+int main() {
+	ios_base::sync_with_stdio(false);
+	cin.tie(NULL);
+	cout.tie(NULL);
+
+	// 입력
+	int n, r, q, root;
+	cin >> n >> r >> q;
+
+	int c = (n - 1);
+	int i, j;
+	while (c--) {
+		cin >> i >> j;
+		edge_v[i].push_back(j);
+		edge_v[j].push_back(i);
+	}
+
+	// 연산
+	makeTree(r, -1);
+	countNode(r);
+
+	// 출력
+	for (int i = 0; i < q; i++) {
+		cin >> root;
+		cout << nodeSize[root] << '\n';
+	}
+
+	return 0;
+}