func_code_string: #include <bits/stdc++.h>   using namespace std;   template <typename T>   void printvec(vector<T>& vec) {     for (int i = 0; i < vec.size(); i++) {       cout << vec[i] <<    ;     }     cout <<   n ;   }   vector<vector<int> > adj;   vector<int> comp;   vector<vector<int> > memb, arr;   vector<vector<long long> > cum;   vector<bool> visited(1000 * 100 + 5, false);   int ctr = 0;   vector<int> dia1, dia2;   vector<vector<int> > dist(2, vector<int>(1000 * 100 + 5, INT_MAX));   vector<int> distmax(1000 * 100 + 5);   vector<int> dialen;   void dfs(int curr, int prev) {     int i;     visited[curr] = true;     comp[curr] = ctr;     for (i = 0; i < adj[curr].size(); i++) {       if (adj[curr][i] == prev) continue;       dfs(adj[curr][i], curr);     }   }   int findend(int a) {     queue<int> q;     int ans;     q.push(a);     visited[a] = true;     while (!q.empty()) {       ans = q.front();       q.pop();       for (int i = 0; i < adj[ans].size(); i++) {         if (!visited[adj[ans][i]]) {           q.push(adj[ans][i]);           visited[adj[ans][i]] = true;         }       }     }     return ans;   }   void applybfs(int a, int type) {     queue<int> q;     int ans;     q.push(a);     visited[a] = true;     dist[type][a] = 0;     while (!q.empty()) {       ans = q.front();       q.pop();       for (int i = 0; i < adj[ans].size(); i++) {         if (!visited[adj[ans][i]]) {           q.push(adj[ans][i]);           visited[adj[ans][i]] = true;           dist[type][adj[ans][i]] = dist[type][ans] + 1;         }       }     }   }   int main() {     int ttt = 1;     while (ttt--) {       int n, m, q, i, j;       scanf( %d%d%d , &n, &m, &q);       adj.resize(n);       comp.resize(n);       for (i = 0; i < m; i++) {         int a, b;         scanf( %d%d , &a, &b);         a--;         b--;         adj[a].push_back(b);         adj[b].push_back(a);       }       for (i = 0; i < n; i++) {         if (!visited[i]) {           dfs(i, -1);           ctr++;         }       }       memb.resize(ctr);       dialen.resize(ctr);       for (i = 0; i < n; i++) memb[comp[i]].push_back(i);       for (i = 0; i < visited.size(); i++) visited[i] = false;       dia1.resize(ctr);       dia2.resize(ctr);       for (i = 0; i < ctr; i++) dia1[i] = findend(memb[i][0]);       for (i = 0; i < visited.size(); i++) visited[i] = false;       for (i = 0; i < ctr; i++) dia2[i] = findend(dia1[i]);       for (i = 0; i < visited.size(); i++) visited[i] = false;       for (i = 0; i < ctr; i++) applybfs(dia1[i], 0);       for (i = 0; i < visited.size(); i++) visited[i] = false;       for (i = 0; i < ctr; i++) applybfs(dia2[i], 1);       for (i = 0; i < ctr; i++) dialen[i] = dist[1][dia1[i]];       arr.resize(ctr);       cum.resize(ctr);       for (i = 0; i < n; i++) arr[comp[i]].push_back(max(dist[0][i], dist[1][i]));       for (i = 0; i < ctr; i++) sort(arr[i].begin(), arr[i].end());       for (i = 0; i < ctr; i++) cum[i].resize(arr[i].size());       for (i = 0; i < ctr; i++) cum[i][0] = arr[i][0];       for (i = 0; i < ctr; i++) {         for (j = 1; j < arr[i].size(); j++) {           cum[i][j] = cum[i][j - 1] + (long long)arr[i][j];         }       }       map<pair<int, int>, double> mapp;       for (int iii = 0; iii < q; iii++) {         int a, b;         scanf( %d%d , &a, &b);         a--;         b--;         if (memb[comp[a]].size() > memb[comp[b]].size()) swap(a, b);         int comp1 = comp[a], comp2 = comp[b];         map<pair<int, int>, double>::iterator it2 =             mapp.find(make_pair(comp1, comp2));         if (it2 != mapp.end()) {           printf( %.20f n , it2->second);           continue;         }         if (comp1 == comp2) {           printf( -1 n );           continue;         }         long long sz1 = memb[comp1].size(), sz2 = memb[comp2].size();         int maxdia = max(dialen[comp1], dialen[comp2]);         vector<int>& vec1 = arr[comp1];         vector<long long>& cum1 = cum[comp1];         vector<int>& vec2 = arr[comp2];         vector<long long>& cum2 = cum[comp2];         long long den = sz1 * sz2;         long long num = 0;         vector<int>::iterator it;         for (i = 0; i < vec1.size(); i++) {           it = upper_bound(vec2.begin(), vec2.end(), maxdia - vec1[i] - 1);           long long temp1 = 0, temp2 = 0;           if (it == vec2.begin()) {             temp1 = 0;             temp2 = ((long long)vec1[i]) * sz2;             temp2 += cum2[cum2.size() - 1];             temp2 += sz2;           } else {             long long abc = it - vec2.begin();             temp1 = maxdia * abc;             long long abc2 = sz2 - abc;             temp2 = ((long long)vec1[i]) * abc2;             temp2 += abc2;             temp2 += (cum2[vec2.size() - 1] - cum2[abc - 1]);           }           num += (temp1 + temp2);         }         double ans = (double)num / den;         mapp[make_pair(comp1, comp2)] = ans;         printf( %.20f n , ans);       }     }     return 0;   }   