BOJ_15270 : 친구 팰린드롬

Author: spring0913

week12/BOJ_15270(친구 팰린드롬).java

@@ -0,0 +1,48 @@
+import java.io.*;
+import java.util.*;
+
+public class Main {
+
+    private static int N, M;
+    private static boolean[][] friend;
+    private static int[][] relation;
+    private static boolean[] visited;
+    private static int answer = 0;
+
+    public static void main(String[] args) throws IOException {
+        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
+        StringTokenizer st = new StringTokenizer(br.readLine());
+        N = Integer.parseInt(st.nextToken());
+        M = Integer.parseInt(st.nextToken());
+        friend = new boolean[N+1][N+1];
+        relation = new int[M][2];
+        visited = new boolean[N+1];
+        for(int i=0; i<M; i++) {
+            st = new StringTokenizer(br.readLine());
+            int u = Integer.parseInt(st.nextToken());
+            int v = Integer.parseInt(st.nextToken());
+            friend[u][v] = true;
+            friend[v][u] = true;
+            relation[i][0] = u;
+            relation[i][1] = v;
+        }
+        dfs(0, 0);
+        System.out.println((answer == N) ? answer : answer + 1);
+    }
+
+    public static void dfs(int start, int count) {
+        answer = Math.max(answer, count);
+
+        for(int i=start; i<M; i++) {
+            int friend1 = relation[i][0];
+            int friend2 = relation[i][1];
+            if(!visited[friend1] && !visited[friend2]) {
+                visited[friend1] = true;
+                visited[friend2] = true;
+                dfs(i, count+2);
+                visited[friend1] = false;
+                visited[friend2] = false;
+            }
+        }
+    }
+}