oj.uz

Submission #851060

# Submission time Handle Problem Language Result Execution time Memory
851060 2023-09-18T11:43:24 Z emkow Network (BOI15_net) C++17
100 / 100
 424 ms 85140 KB 
#include <bits/stdc++.h>
#pragma GCC optimize("O3", "unroll-loops")
#define pb emplace_back
#define ins insert
#define ssize(x) (int)x.size()
#define all(x) x.begin(), x.end()
#define rall(x) x.rbegin(), x.rend()
#define pii pair <int, int>
#define pll pair <ll, ll>
#define pld pair <ld, ld>
#define st first
#define nd second

using namespace std;
using ll = int_fast64_t;
// using lll = __int128_t;
using ld = long double;
const int oo = 1e9 + 7;
const int mod = 1e9 + 7;

void solve(){
    int n; cin >> n;
    vector <int> deg(n, 0);
    vector <vector<int>> g(n);
    for(int i = 1; i < n; i ++){
        int a, b; cin >> a >> b;
        -- a; -- b;
        g[a].pb(b);
        g[b].pb(a);
        deg[a] ++;
        deg[b] ++;
    }
    vector <int> dp(n);
    int cnt = 0, root;
    for(int i = 0; i < n; i ++){
        if(deg[i] == 1){
            ++ cnt;
            dp[i] = 1;
        }
        else root = i;
    }
    function<void(int, int)> cnt_dp = [&](int v, int p){
        for(auto u: g[v]){
            cnt_dp(u, v);
            dp[v] += dp[u];
        }
    };
    function<int(int, int)> find = [&](int v, int p){
        for(auto u: g[v]){
            if(deg[u] != 1 && dp[u] > 2 * cnt){
                dp[v] -= dp[u];
                dp[u] += dp[v];
                find(u, p);
            }
        }
        return v;
    };
    int cent = find(root, -1);
    vector <int> leaves;
    function<void(int, int)> dfs = [&](int v, int p){
        if(deg[v] == 1) leaves.pb(v);
        for(auto u: g[v]){
            if(u == p) continue;
            dfs(u, v);
        }
    };
    dfs(cent, -1);
    int k = ssize(leaves);
    cout << (k + 1) / 2 << '\n';
    for(int i = 0; i < k / 2; i ++) cout << leaves[i] + 1 << ' ' << leaves[i + k / 2] + 1 << '\n';
    if(k & 1) cout << leaves[0] + 1 << ' ' << leaves.back() + 1 << '\n';
}

signed main(){
    ios_base::sync_with_stdio(0); cin.tie(0);
    int t; t = 1;
    // cin >> t;
    while(t --) solve();
    return 0;
}

Compilation message

net.cpp: In function 'void solve()':
net.cpp:34:18: warning: 'root' may be used uninitialized in this function [-Wmaybe-uninitialized]
   34 |     int cnt = 0, root;
      |                  ^~~~

Subtask #1
18.0 / 18.0

# Verdict Execution time Memory Grader output
1 Correct 1 ms 344 KB Output is correct
2 Correct 1 ms 344 KB Output is correct
3 Correct 1 ms 344 KB Output is correct
4 Correct 0 ms 348 KB Output is correct
5 Correct 0 ms 344 KB Output is correct
6 Correct 0 ms 344 KB Output is correct
7 Correct 0 ms 544 KB Output is correct
8 Correct 0 ms 344 KB Output is correct
9 Correct 0 ms 344 KB Output is correct
10 Correct 0 ms 344 KB Output is correct
11 Correct 0 ms 348 KB Output is correct
12 Correct 0 ms 348 KB Output is correct
13 Correct 0 ms 344 KB Output is correct
14 Correct 0 ms 344 KB Output is correct
15 Correct 0 ms 344 KB Output is correct
16 Correct 1 ms 348 KB Output is correct
17 Correct 0 ms 348 KB Output is correct
18 Correct 0 ms 344 KB Output is correct
19 Correct 0 ms 344 KB Output is correct
20 Correct 0 ms 344 KB Output is correct

Subtask #2
45.0 / 45.0

# Verdict Execution time Memory Grader output
1 Correct 1 ms 344 KB Output is correct
2 Correct 1 ms 344 KB Output is correct
3 Correct 1 ms 344 KB Output is correct
4 Correct 0 ms 348 KB Output is correct
5 Correct 0 ms 344 KB Output is correct
6 Correct 0 ms 344 KB Output is correct
7 Correct 0 ms 544 KB Output is correct
8 Correct 0 ms 344 KB Output is correct
9 Correct 0 ms 344 KB Output is correct
10 Correct 0 ms 344 KB Output is correct
11 Correct 0 ms 348 KB Output is correct
12 Correct 0 ms 348 KB Output is correct
13 Correct 0 ms 344 KB Output is correct
14 Correct 0 ms 344 KB Output is correct
15 Correct 0 ms 344 KB Output is correct
16 Correct 1 ms 348 KB Output is correct
17 Correct 0 ms 348 KB Output is correct
18 Correct 0 ms 344 KB Output is correct
19 Correct 0 ms 344 KB Output is correct
20 Correct 0 ms 344 KB Output is correct
21 Correct 1 ms 344 KB Output is correct
22 Correct 1 ms 600 KB Output is correct
23 Correct 1 ms 600 KB Output is correct
24 Correct 1 ms 600 KB Output is correct
25 Correct 1 ms 600 KB Output is correct
26 Correct 1 ms 344 KB Output is correct
27 Correct 1 ms 600 KB Output is correct
28 Correct 1 ms 600 KB Output is correct
29 Correct 1 ms 344 KB Output is correct
30 Correct 0 ms 348 KB Output is correct
31 Correct 1 ms 600 KB Output is correct
32 Correct 0 ms 344 KB Output is correct
33 Correct 1 ms 544 KB Output is correct
34 Correct 0 ms 348 KB Output is correct
35 Correct 0 ms 344 KB Output is correct
36 Correct 0 ms 344 KB Output is correct
37 Correct 1 ms 344 KB Output is correct
38 Correct 1 ms 344 KB Output is correct
39 Correct 0 ms 348 KB Output is correct
40 Correct 0 ms 344 KB Output is correct
41 Correct 1 ms 344 KB Output is correct
42 Correct 1 ms 344 KB Output is correct
43 Correct 1 ms 344 KB Output is correct
44 Correct 0 ms 344 KB Output is correct
45 Correct 1 ms 344 KB Output is correct
46 Correct 1 ms 344 KB Output is correct
47 Correct 0 ms 344 KB Output is correct
48 Correct 0 ms 344 KB Output is correct
49 Correct 1 ms 344 KB Output is correct
50 Correct 1 ms 344 KB Output is correct
51 Correct 0 ms 348 KB Output is correct
52 Correct 0 ms 344 KB Output is correct
53 Correct 1 ms 344 KB Output is correct
54 Correct 0 ms 348 KB Output is correct
55 Correct 0 ms 344 KB Output is correct
56 Correct 1 ms 348 KB Output is correct
57 Correct 0 ms 344 KB Output is correct
58 Correct 1 ms 600 KB Output is correct

Subtask #3
37.0 / 37.0

# Verdict Execution time Memory Grader output
1 Correct 1 ms 344 KB Output is correct
2 Correct 1 ms 344 KB Output is correct
3 Correct 1 ms 344 KB Output is correct
4 Correct 0 ms 348 KB Output is correct
5 Correct 0 ms 344 KB Output is correct
6 Correct 0 ms 344 KB Output is correct
7 Correct 0 ms 544 KB Output is correct
8 Correct 0 ms 344 KB Output is correct
9 Correct 0 ms 344 KB Output is correct
10 Correct 0 ms 344 KB Output is correct
11 Correct 0 ms 348 KB Output is correct
12 Correct 0 ms 348 KB Output is correct
13 Correct 0 ms 344 KB Output is correct
14 Correct 0 ms 344 KB Output is correct
15 Correct 0 ms 344 KB Output is correct
16 Correct 1 ms 348 KB Output is correct
17 Correct 0 ms 348 KB Output is correct
18 Correct 0 ms 344 KB Output is correct
19 Correct 0 ms 344 KB Output is correct
20 Correct 0 ms 344 KB Output is correct
21 Correct 1 ms 344 KB Output is correct
22 Correct 1 ms 600 KB Output is correct
23 Correct 1 ms 600 KB Output is correct
24 Correct 1 ms 600 KB Output is correct
25 Correct 1 ms 600 KB Output is correct
26 Correct 1 ms 344 KB Output is correct
27 Correct 1 ms 600 KB Output is correct
28 Correct 1 ms 600 KB Output is correct
29 Correct 1 ms 344 KB Output is correct
30 Correct 0 ms 348 KB Output is correct
31 Correct 1 ms 600 KB Output is correct
32 Correct 0 ms 344 KB Output is correct
33 Correct 1 ms 544 KB Output is correct
34 Correct 0 ms 348 KB Output is correct
35 Correct 0 ms 344 KB Output is correct
36 Correct 0 ms 344 KB Output is correct
37 Correct 1 ms 344 KB Output is correct
38 Correct 1 ms 344 KB Output is correct
39 Correct 0 ms 348 KB Output is correct
40 Correct 0 ms 344 KB Output is correct
41 Correct 1 ms 344 KB Output is correct
42 Correct 1 ms 344 KB Output is correct
43 Correct 1 ms 344 KB Output is correct
44 Correct 0 ms 344 KB Output is correct
45 Correct 1 ms 344 KB Output is correct
46 Correct 1 ms 344 KB Output is correct
47 Correct 0 ms 344 KB Output is correct
48 Correct 0 ms 344 KB Output is correct
49 Correct 1 ms 344 KB Output is correct
50 Correct 1 ms 344 KB Output is correct
51 Correct 0 ms 348 KB Output is correct
52 Correct 0 ms 344 KB Output is correct
53 Correct 1 ms 344 KB Output is correct
54 Correct 0 ms 348 KB Output is correct
55 Correct 0 ms 344 KB Output is correct
56 Correct 1 ms 348 KB Output is correct
57 Correct 0 ms 344 KB Output is correct
58 Correct 1 ms 600 KB Output is correct
59 Correct 262 ms 38700 KB Output is correct
60 Correct 347 ms 42816 KB Output is correct
61 Correct 1 ms 500 KB Output is correct
62 Correct 0 ms 344 KB Output is correct
63 Correct 216 ms 34372 KB Output is correct
64 Correct 2 ms 1112 KB Output is correct
65 Correct 9 ms 3416 KB Output is correct
66 Correct 79 ms 24400 KB Output is correct
67 Correct 408 ms 85140 KB Output is correct
68 Correct 424 ms 70300 KB Output is correct
69 Correct 5 ms 1816 KB Output is correct
70 Correct 51 ms 14664 KB Output is correct
71 Correct 210 ms 45944 KB Output is correct
72 Correct 229 ms 44600 KB Output is correct
73 Correct 41 ms 11728 KB Output is correct
74 Correct 346 ms 41980 KB Output is correct
75 Correct 15 ms 5336 KB Output is correct
76 Correct 222 ms 45596 KB Output is correct
77 Correct 213 ms 45596 KB Output is correct
78 Correct 16 ms 6336 KB Output is correct
79 Correct 382 ms 59728 KB Output is correct
80 Correct 2 ms 600 KB Output is correct
81 Correct 57 ms 14924 KB Output is correct
82 Correct 298 ms 43440 KB Output is correct
83 Correct 325 ms 41668 KB Output is correct
84 Correct 304 ms 41712 KB Output is correct
85 Correct 298 ms 41560 KB Output is correct
86 Correct 332 ms 42696 KB Output is correct
87 Correct 333 ms 42704 KB Output is correct