meituan-008. 小团无路可逃

src/main/java/study/plan/meituan/meituan008/Solution.java

@@ -0,0 +1,127 @@
+package study.plan.meituan.meituan008;
+
+import java.io.*;
+import java.util.*;
+
+public class Solution {
+
+    static Scanner sc;
+    static PrintWriter pw;
+
+    public static void main(String[] args) throws IOException {
+        sc = new Scanner(System.in);
+        pw = new PrintWriter(System.out);
+        solve();
+        pw.close();
+    }
+
+    public static void solve() throws IOException {
+        int n = sc.nextInt();
+        int m = sc.nextInt();
+        int t = sc.nextInt();
+        int[][] mat = new int[n - 1][2];
+        for (int i = 0; i < mat.length; i++) {
+            mat[i] = sc.nextIntArr(2);
+        }
+        list = new ArrayList<>();
+        for (int i = 0; i < n + 1; i++) {
+            list.add(new ArrayList<>());
+        }
+        for (int i = 0; i < n - 1; i++) {
+            int x = mat[i][0];
+            int y = mat[i][1];
+            list.get(x).add(y);
+            list.get(y).add(x);
+        }
+
+        mdis = new int[n + 1];
+        Arrays.fill(mdis, -1);
+        tdis = new int[n + 1];
+        Arrays.fill(tdis, -1);
+        dism(m);
+        dist(t);
+        int res = 0;
+        for (int i = 1; i <= n; i++) {
+            if (mdis[i] > tdis[i]) res = Math.max(res, mdis[i]);
+        }
+        pw.println(res);
+    }
+
+    static List<List<Integer>> list;
+    static int[] mdis;
+    static int[] tdis;
+
+    public static void dism(int index) {
+        Deque<Integer> deque = new ArrayDeque<>();
+        deque.add(index);
+        int t;
+        mdis[index] = 0;
+        while (!deque.isEmpty()) {
+            t = deque.removeFirst();
+            List<Integer> templist = list.get(t);
+            for (int i = 0; i < templist.size(); i++) {
+                if (mdis[templist.get(i)] == -1) {
+                    mdis[templist.get(i)] = mdis[t] + 1;
+                    deque.add(templist.get(i));
+                }
+            }
+        }
+    }
+
+    public static void dist(int index) {
+        Deque<Integer> deque = new ArrayDeque<>();
+        deque.add(index);
+        int t;
+        tdis[index] = 0;
+        while (!deque.isEmpty()) {
+            t = deque.removeFirst();
+            List<Integer> templist = list.get(t);
+            for (int i = 0; i < templist.size(); i++) {
+                if (tdis[templist.get(i)] == -1) {
+                    tdis[templist.get(i)] = tdis[t] + 1;
+                    deque.add(templist.get(i));
+                }
+            }
+        }
+    }
+
+    static class Scanner {
+        BufferedReader br;
+        StringTokenizer st;
+
+        public Scanner(InputStream s) {
+            br = new BufferedReader(new InputStreamReader(s));
+        }
+
+        public Scanner(FileReader f) {
+            br = new BufferedReader(f);
+        }
+
+        public String next() throws IOException {
+            while (st == null || !st.hasMoreTokens())
+                st = new StringTokenizer(br.readLine());
+            return st.nextToken();
+        }
+
+        public int nextInt() throws IOException {
+            return Integer.parseInt(next());
+        }
+
+        public long nextLong() throws IOException {
+            return Long.parseLong(next());
+        }
+
+        public double nextDouble() throws IOException {
+            return Double.parseDouble(next());
+        }
+
+        public int[] nextIntArr(int n) throws IOException {
+            int[] arr = new int[n];
+            for (int i = 0; i < n; i++) {
+                arr[i] = Integer.parseInt(next());
+            }
+            return arr;
+        }
+
+    }
+}