git reimport

archive/2016.09/2016.09.19 - unsorted/L.java

@@ -0,0 +1,73 @@
+package chelper;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.LinkedList;
+import java.util.List;
+import java.util.Queue;
+
+import io.InputReader;
+import io.OutputWriter;
+
+public class L {
+  int[] bfs(List<List<Integer>> edges, int from) {
+    int n = edges.size();
+    int[] res = new int[n];
+    Arrays.fill(res, n + 100);
+    res[from] = 0;
+
+    boolean[] visited = new boolean[n];
+    visited[from] = true;
+
+    Queue<Integer> queue = new LinkedList<>();
+    queue.add(from);
+
+    while (!queue.isEmpty()) {
+      int a = queue.poll();
+      for (int b : edges.get(a)) {
+        if (!visited[b]) {
+          res[b] = res[a] + 1;
+          visited[b] = true;
+          queue.add(b);
+        }
+      }
+    }
+
+    return res;
+  }
+
+  public void solve(int testNumber, InputReader in, OutputWriter out) {
+    int n = in.nextInt() + 1;
+    int m = in.nextInt();
+
+    int a = in.nextInt();
+    int b = in.nextInt();
+
+    List<List<Integer>> edges1 = new ArrayList<>();
+    List<List<Integer>> edges2 = new ArrayList<>();
+
+    for (int i = 0; i < n; i++) {
+      edges1.add(new ArrayList<>());
+      edges2.add(new ArrayList<>());
+    }
+
+    for (int i = 0; i < m; i++) {
+      int v1 = in.nextInt();
+      int v2 = in.nextInt();
+      edges1.get(v1).add(v2);
+      edges2.get(v2).add(v1);
+    }
+
+    int[] toPivot = bfs(edges1, 0);
+    int[] fromA = bfs(edges2, a);
+    int[] fromB = bfs(edges2, b);
+
+    int res = n + 100;
+
+    for (int i = 0; i < n; i++) {
+      res = Math.min(res, toPivot[i] + fromA[i] + fromB[i]);
+    }
+
+    out.println(res);
+  }
+}