git reimport

archive/2017.09/2017.09.19 - unsorted/B.java

@@ -0,0 +1,65 @@
+package chelper;
+
+import java.util.ArrayList;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Set;
+
+import io.InputReader;
+import io.OutputWriter;
+import misc.SimpleSavingChelperSolution;
+
+
+public class B extends SimpleSavingChelperSolution {
+
+  public void solve(int testNumber, InputReader in, OutputWriter out) {
+    wrapSolve(testNumber, in, out);
+  }
+
+  int n;
+  List<List<Integer>> edges;
+  long c1 = 0;
+  long c2 = 0;
+  Set<Integer> visited;
+
+  @Override
+  public void solve(int testNumber) {
+    n = in.nextInt();
+
+    edges = new ArrayList<>();
+    for (int i = 0; i < n; i++) {
+      edges.add(new ArrayList<>());
+    }
+
+
+    for (int i = 0; i < n - 1; i++) {
+      int a = in.nextInt() - 1;
+      int b = in.nextInt() - 1;
+
+      edges.get(a).add(b);
+      edges.get(b).add(a);
+    }
+
+    visited = new HashSet<>();
+    dfs(0, true);
+
+    long total = c1 * c2 - (n - 1);
+    out.println(total);
+  }
+
+  void dfs(int v, boolean color) {
+    visited.add(v);
+    if (color) {
+      c1++;
+    } else {
+      c2++;
+    }
+
+    for (Integer o : edges.get(v)) {
+      if (visited.contains(o)) {
+        continue;
+      }
+      dfs(o, !color);
+    }
+  }
+}