diff --git "a/zinnnn37/202509/5 BOJ G3 2533 \354\202\254\355\232\214\353\247\235 \354\204\234\353\271\204\354\212\244(SNS).md" "b/zinnnn37/202509/5 BOJ G3 2533 \354\202\254\355\232\214\353\247\235 \354\204\234\353\271\204\354\212\244(SNS).md" new file mode 100644 index 00000000..c28f962b --- /dev/null +++ "b/zinnnn37/202509/5 BOJ G3 2533 \354\202\254\355\232\214\353\247\235 \354\204\234\353\271\204\354\212\244(SNS).md" @@ -0,0 +1,73 @@ +```java +import java.io.BufferedReader; +import java.io.BufferedWriter; +import java.io.IOException; +import java.io.InputStreamReader; +import java.io.OutputStreamWriter; +import java.util.ArrayList; +import java.util.List; +import java.util.StringTokenizer; + +public class BJ_2533_사회망_서비스_SNS { + + private static BufferedReader br = new BufferedReader(new InputStreamReader(System.in)); + private static BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out)); + private static StringTokenizer st; + + private static int N; + private static int[][] dp; // [노드][0(일반인)/1(얼리어답터)] + + private static boolean[] visited; + private static List[] tree; + + public static void main(String[] args) throws IOException { + init(); + sol(); + } + + private static void init() throws IOException { + N = Integer.parseInt(br.readLine()); + + tree = new List[N + 1]; + for (int i = 1; i <= N; i++) { + tree[i] = new ArrayList<>(); + } + + for (int i = 0; i < N - 1; i++) { + st = new StringTokenizer(br.readLine()); + + int u = Integer.parseInt(st.nextToken()); + int v = Integer.parseInt(st.nextToken()); + + tree[u].add(v); + tree[v].add(u); + } + visited = new boolean[N + 1]; + dp = new int[N + 1][2]; + } + + private static void sol() throws IOException { + find(1); + + bw.write(Math.min(dp[1][0], dp[1][1]) + ""); + bw.flush(); + bw.close(); + br.close(); + } + + private static void find(int u) { + visited[u] = true; + dp[u][0] = 1; // 초기화: 필요한 얼리어답터 수 = 1 + + for (int v : tree[u]) { + if (visited[v]) { + continue; + } + find(v); + dp[u][1] += dp[v][0]; // 내가 얼리어답터면 친구가 얼리어답터일 필요 없음 + dp[u][0] += Math.min(dp[v][0], dp[v][1]); + } + } + +} +``` \ No newline at end of file