oj.uz

Submission #53927

# Submission time Handle Problem Language Result Execution time Memory
53927 2018-07-01T22:14:00 Z ruhanhabib39 Network (BOI15_net) C++17
100 / 100
 840 ms 155956 KB 
#include <bits/stdc++.h>
using namespace std;

const int MAXN = 5e5;

int n;
vector<int> G[MAXN + 10];

vector<pair<int,int>> edges;
bool done[MAXN + 10];
int sz[MAXN + 10];

void dfs1(int u, int p = -1) {
   for(int v : G[u]) {
      if(v != p) dfs1(v, u);
   }
   sz[u] = 0;
   if((int)G[u].size() == 1) {
      sz[u] = 1;
   }
   for(int v : G[u]) {
      if(v != p) sz[u] += sz[v];
   }
   return;
}

int lc = 0;
int dfs2(int u, int p = -1) {
   for(int v : G[u]) {
      if(v != p && sz[v] > (lc+1)/2) return dfs2(v, u);
   }
   return u;
}
int centroid(int u) {
   dfs1(u); lc = sz[u];
   return dfs2(u);
}

void work() {
   int root = 1;
   while((int)G[root].size() == 1) ++root;
   root = centroid(root);
   vector<int> leaves;
   for(int v : G[root]) {
      function<void(int,int)> dfs = [&](int u, int p) {
         if((int)G[u].size() == 1) {
            leaves.push_back(u);
         }
         for(int w : G[u]) {
            if(w != p) dfs(w, u);
         }
      };
      dfs(v, root);
   }
   for(int i = 0; i < lc/2; i++) {
      edges.emplace_back(leaves[i], leaves[i + (lc + 1)/2]);
   }
   if(lc & 1) {
      edges.emplace_back(leaves[(lc+1)/2-1], root);
   }
}

int main() {
   scanf("%d", &n);
   for(int i = 1; i < n; i++) {
      int u, v; scanf("%d%d", &u, &v);
      G[u].push_back(v);
      G[v].push_back(u);
   }
   work();
   printf("%d\n", (int)edges.size());
   for(auto it : edges) printf("%d %d\n", it.first, it.second);
}

Compilation message

net.cpp: In function 'int main()':
net.cpp:64:9: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
    scanf("%d", &n);
    ~~~~~^~~~~~~~~~
net.cpp:66:22: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
       int u, v; scanf("%d%d", &u, &v);
                 ~~~~~^~~~~~~~~~~~~~~~

Subtask #1
18.0 / 18.0

# Verdict Execution time Memory Grader output
1 Correct 14 ms 11992 KB Output is correct
2 Correct 12 ms 12144 KB Output is correct
3 Correct 12 ms 12144 KB Output is correct
4 Correct 17 ms 12144 KB Output is correct
5 Correct 14 ms 12256 KB Output is correct
6 Correct 12 ms 12256 KB Output is correct
7 Correct 11 ms 12256 KB Output is correct
8 Correct 13 ms 12256 KB Output is correct
9 Correct 11 ms 12308 KB Output is correct
10 Correct 12 ms 12476 KB Output is correct
11 Correct 12 ms 12476 KB Output is correct
12 Correct 11 ms 12476 KB Output is correct
13 Correct 12 ms 12476 KB Output is correct
14 Correct 12 ms 12476 KB Output is correct
15 Correct 12 ms 12476 KB Output is correct
16 Correct 13 ms 12476 KB Output is correct
17 Correct 11 ms 12476 KB Output is correct
18 Correct 11 ms 12476 KB Output is correct
19 Correct 13 ms 12476 KB Output is correct
20 Correct 12 ms 12476 KB Output is correct

Subtask #2
45.0 / 45.0

# Verdict Execution time Memory Grader output
1 Correct 14 ms 11992 KB Output is correct
2 Correct 12 ms 12144 KB Output is correct
3 Correct 12 ms 12144 KB Output is correct
4 Correct 17 ms 12144 KB Output is correct
5 Correct 14 ms 12256 KB Output is correct
6 Correct 12 ms 12256 KB Output is correct
7 Correct 11 ms 12256 KB Output is correct
8 Correct 13 ms 12256 KB Output is correct
9 Correct 11 ms 12308 KB Output is correct
10 Correct 12 ms 12476 KB Output is correct
11 Correct 12 ms 12476 KB Output is correct
12 Correct 11 ms 12476 KB Output is correct
13 Correct 12 ms 12476 KB Output is correct
14 Correct 12 ms 12476 KB Output is correct
15 Correct 12 ms 12476 KB Output is correct
16 Correct 13 ms 12476 KB Output is correct
17 Correct 11 ms 12476 KB Output is correct
18 Correct 11 ms 12476 KB Output is correct
19 Correct 13 ms 12476 KB Output is correct
20 Correct 12 ms 12476 KB Output is correct
21 Correct 11 ms 12476 KB Output is correct
22 Correct 12 ms 12576 KB Output is correct
23 Correct 12 ms 12636 KB Output is correct
24 Correct 13 ms 12696 KB Output is correct
25 Correct 13 ms 12696 KB Output is correct
26 Correct 12 ms 12696 KB Output is correct
27 Correct 14 ms 12696 KB Output is correct
28 Correct 13 ms 12700 KB Output is correct
29 Correct 12 ms 12700 KB Output is correct
30 Correct 13 ms 12736 KB Output is correct
31 Correct 15 ms 12744 KB Output is correct
32 Correct 13 ms 12744 KB Output is correct
33 Correct 14 ms 12744 KB Output is correct
34 Correct 12 ms 12744 KB Output is correct
35 Correct 14 ms 12744 KB Output is correct
36 Correct 12 ms 12744 KB Output is correct
37 Correct 12 ms 12800 KB Output is correct
38 Correct 11 ms 12824 KB Output is correct
39 Correct 12 ms 12824 KB Output is correct
40 Correct 11 ms 12836 KB Output is correct
41 Correct 12 ms 12836 KB Output is correct
42 Correct 12 ms 12836 KB Output is correct
43 Correct 13 ms 12880 KB Output is correct
44 Correct 12 ms 12880 KB Output is correct
45 Correct 12 ms 12880 KB Output is correct
46 Correct 12 ms 12896 KB Output is correct
47 Correct 11 ms 12896 KB Output is correct
48 Correct 11 ms 12896 KB Output is correct
49 Correct 13 ms 12912 KB Output is correct
50 Correct 13 ms 12912 KB Output is correct
51 Correct 60 ms 12912 KB Output is correct
52 Correct 14 ms 12912 KB Output is correct
53 Correct 12 ms 12936 KB Output is correct
54 Correct 11 ms 12936 KB Output is correct
55 Correct 12 ms 12936 KB Output is correct
56 Correct 12 ms 12936 KB Output is correct
57 Correct 13 ms 12936 KB Output is correct
58 Correct 12 ms 12964 KB Output is correct

Subtask #3
37.0 / 37.0

# Verdict Execution time Memory Grader output
1 Correct 14 ms 11992 KB Output is correct
2 Correct 12 ms 12144 KB Output is correct
3 Correct 12 ms 12144 KB Output is correct
4 Correct 17 ms 12144 KB Output is correct
5 Correct 14 ms 12256 KB Output is correct
6 Correct 12 ms 12256 KB Output is correct
7 Correct 11 ms 12256 KB Output is correct
8 Correct 13 ms 12256 KB Output is correct
9 Correct 11 ms 12308 KB Output is correct
10 Correct 12 ms 12476 KB Output is correct
11 Correct 12 ms 12476 KB Output is correct
12 Correct 11 ms 12476 KB Output is correct
13 Correct 12 ms 12476 KB Output is correct
14 Correct 12 ms 12476 KB Output is correct
15 Correct 12 ms 12476 KB Output is correct
16 Correct 13 ms 12476 KB Output is correct
17 Correct 11 ms 12476 KB Output is correct
18 Correct 11 ms 12476 KB Output is correct
19 Correct 13 ms 12476 KB Output is correct
20 Correct 12 ms 12476 KB Output is correct
21 Correct 11 ms 12476 KB Output is correct
22 Correct 12 ms 12576 KB Output is correct
23 Correct 12 ms 12636 KB Output is correct
24 Correct 13 ms 12696 KB Output is correct
25 Correct 13 ms 12696 KB Output is correct
26 Correct 12 ms 12696 KB Output is correct
27 Correct 14 ms 12696 KB Output is correct
28 Correct 13 ms 12700 KB Output is correct
29 Correct 12 ms 12700 KB Output is correct
30 Correct 13 ms 12736 KB Output is correct
31 Correct 15 ms 12744 KB Output is correct
32 Correct 13 ms 12744 KB Output is correct
33 Correct 14 ms 12744 KB Output is correct
34 Correct 12 ms 12744 KB Output is correct
35 Correct 14 ms 12744 KB Output is correct
36 Correct 12 ms 12744 KB Output is correct
37 Correct 12 ms 12800 KB Output is correct
38 Correct 11 ms 12824 KB Output is correct
39 Correct 12 ms 12824 KB Output is correct
40 Correct 11 ms 12836 KB Output is correct
41 Correct 12 ms 12836 KB Output is correct
42 Correct 12 ms 12836 KB Output is correct
43 Correct 13 ms 12880 KB Output is correct
44 Correct 12 ms 12880 KB Output is correct
45 Correct 12 ms 12880 KB Output is correct
46 Correct 12 ms 12896 KB Output is correct
47 Correct 11 ms 12896 KB Output is correct
48 Correct 11 ms 12896 KB Output is correct
49 Correct 13 ms 12912 KB Output is correct
50 Correct 13 ms 12912 KB Output is correct
51 Correct 60 ms 12912 KB Output is correct
52 Correct 14 ms 12912 KB Output is correct
53 Correct 12 ms 12936 KB Output is correct
54 Correct 11 ms 12936 KB Output is correct
55 Correct 12 ms 12936 KB Output is correct
56 Correct 12 ms 12936 KB Output is correct
57 Correct 13 ms 12936 KB Output is correct
58 Correct 12 ms 12964 KB Output is correct
59 Correct 501 ms 39584 KB Output is correct
60 Correct 594 ms 48264 KB Output is correct
61 Correct 12 ms 48264 KB Output is correct
62 Correct 11 ms 48264 KB Output is correct
63 Correct 411 ms 49636 KB Output is correct
64 Correct 15 ms 49636 KB Output is correct
65 Correct 28 ms 49636 KB Output is correct
66 Correct 204 ms 52980 KB Output is correct
67 Correct 788 ms 78664 KB Output is correct
68 Correct 840 ms 86172 KB Output is correct
69 Correct 19 ms 86172 KB Output is correct
70 Correct 109 ms 86172 KB Output is correct
71 Correct 410 ms 86172 KB Output is correct
72 Correct 445 ms 86312 KB Output is correct
73 Correct 141 ms 86312 KB Output is correct
74 Correct 580 ms 91112 KB Output is correct
75 Correct 44 ms 91112 KB Output is correct
76 Correct 481 ms 102336 KB Output is correct
77 Correct 379 ms 109100 KB Output is correct
78 Correct 101 ms 109100 KB Output is correct
79 Correct 787 ms 127216 KB Output is correct
80 Correct 14 ms 127216 KB Output is correct
81 Correct 133 ms 127216 KB Output is correct
82 Correct 552 ms 127216 KB Output is correct
83 Correct 640 ms 127492 KB Output is correct
84 Correct 616 ms 134384 KB Output is correct
85 Correct 601 ms 140876 KB Output is correct
86 Correct 580 ms 149252 KB Output is correct
87 Correct 626 ms 155956 KB Output is correct