Solved problem 839C from codeforces

Author: AliOsm

CodeForces/839C. Journey.cpp

@@ -0,0 +1,43 @@
+/*
+  Idea:
+    - DFS and calculate the answer.
+*/
+
+#include <bits/stdc++.h>
+
+using namespace std;
+
+int const N = 1e5 + 1;
+bool vis[N];
+int n;
+vector<vector<int> > g;
+
+double rec(int u, int p) {
+  vis[u] = true;
+
+  double ret = 0, prop = 1.0 / (g[u].size() - (p != -1));
+  for(int i = 0, v; i < g[u].size(); ++i) {
+    v = g[u][i];
+
+    if(!vis[v])
+      ret += (rec(v, u) + 1) * prop;
+  }
+
+  return ret;
+}
+
+int main() {
+  scanf("%d", &n);
+  g.resize(n);
+  for(int i = 0, a, b; i < n - 1; ++i) {
+    scanf("%d %d", &a, &b);
+    --a, --b;
+    g[a].push_back(b);
+    swap(a, b);
+    g[a].push_back(b);
+  }
+
+  printf("%.10lf\n", rec(0, -1));
+
+  return 0;
+}

CodeForces/README.md

@@ -378,6 +378,7 @@
 - [837A. Text Volume](http://codeforces.com/contest/837/problem/A)
 - [837B. Flag of Berland](http://codeforces.com/contest/837/problem/B)
 - [837C. Two Seals](http://codeforces.com/contest/837/problem/C)
+- [839C. Journey](http://codeforces.com/contest/839/problem/C)
 - [842A. Kirill And The Game](http://codeforces.com/contest/842/problem/A)
 - [842B. Gleb And Pizza](http://codeforces.com/contest/842/problem/B)
 - [845A. Chess Tourney](http://codeforces.com/contest/845/problem/A)