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Submission #1097709

# Submission time Handle Problem Language Result Execution time Memory
1097709 2024-10-08T03:30:06 Z TrinhKhanhDung Network (BOI15_net) C++14
100 / 100
 264 ms 47952 KB 
#include <bits/stdc++.h>
#define ll long long
#define fi first
#define se second
#define sz(x) (int)x.size()
#define ALL(v) v.begin(),v.end()
#define MASK(k) (1LL << (k))
#define BIT(x, i) (((x) >> (i)) & 1)
#define oo (ll)1e18
#define INF (ll)1e9
#define MOD (ll)(1e9 + 7)

using namespace std;

template<class T1, class T2>
    bool maximize(T1 &a, T2 b){if(a < b){a = b; return true;} return false;}

template<class T1, class T2>
    bool minimize(T1 &a, T2 b){if(a > b){a = b; return true;} return false;}

template<class T1, class T2>
    void add(T1 &a, T2 b){a += b; if(a >= MOD) a -= MOD;}

template<class T1, class T2>
    void sub(T1 &a, T2 b){a -= b; if(a < 0) a += MOD;}

template<class T>
    void cps(T &v){sort(ALL(v)); v.resize(unique(ALL(v)) - v.begin());}

const int MAX = 5e5 + 10;

int N;
vector<int> adj[MAX];
vector<int> leaves;

void dfs(int u, int p = -1){
    if(sz(adj[u]) == 1) leaves.push_back(u);
    for(int v: adj[u]){
        if(v == p) continue;
        dfs(v, u);
    }
}

void solve(){
    cin >> N;
    for(int i = 1; i < N; i++){
        int u, v; cin >> u >> v;
        adj[u].push_back(v);
        adj[v].push_back(u);
    }

    clock_t start = clock();

    if(N == 2){
        cout << 1 << '\n' << "1 2\n";
        return;
    }

    int root;
    for(int i = 1; i <= N; i++){
        if(sz(adj[i]) > 1){
            root = i;
            break;
        }
    }

    dfs(root);

    vector<pair<int, int>> ans;
    int n = sz(leaves);
    for(int i = 0; i < n / 2; i++){
        ans.push_back({leaves[i], leaves[i + n / 2]});
    }

    if(sz(leaves) & 1){
        ans.push_back({leaves[0], leaves.back()});
    }

    cout << sz(ans) << '\n';
    for(auto o: ans){
        cout << o.fi << ' ' << o.se << '\n';
    }

    cerr << "Time elapsed: " << clock() - start << " ms\n";
}

int main(){
    ios_base::sync_with_stdio(0); cin.tie(0);
//    freopen("walk.inp","r",stdin);
//    freopen("walk.out","w",stdout);

    int t = 1;
//    cin >> t;
    while(t--)
        solve();

    return 0;
}

Compilation message

net.cpp: In function 'void solve()':
net.cpp:67:8: warning: 'root' may be used uninitialized in this function [-Wmaybe-uninitialized]
   67 |     dfs(root);
      |     ~~~^~~~~~

Subtask #1
18.0 / 18.0

# Verdict Execution time Memory Grader output
1 Correct 6 ms 12124 KB Output is correct
2 Correct 5 ms 12124 KB Output is correct
3 Correct 6 ms 12124 KB Output is correct
4 Correct 5 ms 12376 KB Output is correct
5 Correct 6 ms 12124 KB Output is correct
6 Correct 6 ms 12124 KB Output is correct
7 Correct 5 ms 12124 KB Output is correct
8 Correct 6 ms 12124 KB Output is correct
9 Correct 6 ms 12124 KB Output is correct
10 Correct 5 ms 12120 KB Output is correct
11 Correct 5 ms 12124 KB Output is correct
12 Correct 6 ms 12124 KB Output is correct
13 Correct 6 ms 12124 KB Output is correct
14 Correct 5 ms 12120 KB Output is correct
15 Correct 6 ms 12124 KB Output is correct
16 Correct 5 ms 12124 KB Output is correct
17 Correct 5 ms 12196 KB Output is correct
18 Correct 5 ms 12120 KB Output is correct
19 Correct 5 ms 12124 KB Output is correct
20 Correct 5 ms 12124 KB Output is correct

Subtask #2
45.0 / 45.0

# Verdict Execution time Memory Grader output
1 Correct 6 ms 12124 KB Output is correct
2 Correct 5 ms 12124 KB Output is correct
3 Correct 6 ms 12124 KB Output is correct
4 Correct 5 ms 12376 KB Output is correct
5 Correct 6 ms 12124 KB Output is correct
6 Correct 6 ms 12124 KB Output is correct
7 Correct 5 ms 12124 KB Output is correct
8 Correct 6 ms 12124 KB Output is correct
9 Correct 6 ms 12124 KB Output is correct
10 Correct 5 ms 12120 KB Output is correct
11 Correct 5 ms 12124 KB Output is correct
12 Correct 6 ms 12124 KB Output is correct
13 Correct 6 ms 12124 KB Output is correct
14 Correct 5 ms 12120 KB Output is correct
15 Correct 6 ms 12124 KB Output is correct
16 Correct 5 ms 12124 KB Output is correct
17 Correct 5 ms 12196 KB Output is correct
18 Correct 5 ms 12120 KB Output is correct
19 Correct 5 ms 12124 KB Output is correct
20 Correct 5 ms 12124 KB Output is correct
21 Correct 6 ms 12120 KB Output is correct
22 Correct 5 ms 12124 KB Output is correct
23 Correct 5 ms 12124 KB Output is correct
24 Correct 5 ms 12124 KB Output is correct
25 Correct 6 ms 12124 KB Output is correct
26 Correct 6 ms 12124 KB Output is correct
27 Correct 6 ms 12124 KB Output is correct
28 Correct 7 ms 12120 KB Output is correct
29 Correct 6 ms 12124 KB Output is correct
30 Correct 6 ms 12124 KB Output is correct
31 Correct 5 ms 12124 KB Output is correct
32 Correct 6 ms 12124 KB Output is correct
33 Correct 5 ms 12124 KB Output is correct
34 Correct 7 ms 12196 KB Output is correct
35 Correct 6 ms 12376 KB Output is correct
36 Correct 5 ms 12124 KB Output is correct
37 Correct 5 ms 12124 KB Output is correct
38 Correct 7 ms 12216 KB Output is correct
39 Correct 5 ms 12124 KB Output is correct
40 Correct 4 ms 12204 KB Output is correct
41 Correct 5 ms 12124 KB Output is correct
42 Correct 5 ms 12124 KB Output is correct
43 Correct 5 ms 12124 KB Output is correct
44 Correct 5 ms 12196 KB Output is correct
45 Correct 6 ms 12376 KB Output is correct
46 Correct 5 ms 12120 KB Output is correct
47 Correct 5 ms 12124 KB Output is correct
48 Correct 5 ms 12124 KB Output is correct
49 Correct 6 ms 12140 KB Output is correct
50 Correct 5 ms 12124 KB Output is correct
51 Correct 6 ms 12124 KB Output is correct
52 Correct 5 ms 12124 KB Output is correct
53 Correct 5 ms 12124 KB Output is correct
54 Correct 5 ms 12120 KB Output is correct
55 Correct 5 ms 12124 KB Output is correct
56 Correct 5 ms 12124 KB Output is correct
57 Correct 5 ms 12120 KB Output is correct
58 Correct 5 ms 12124 KB Output is correct

Subtask #3
37.0 / 37.0

# Verdict Execution time Memory Grader output
1 Correct 6 ms 12124 KB Output is correct
2 Correct 5 ms 12124 KB Output is correct
3 Correct 6 ms 12124 KB Output is correct
4 Correct 5 ms 12376 KB Output is correct
5 Correct 6 ms 12124 KB Output is correct
6 Correct 6 ms 12124 KB Output is correct
7 Correct 5 ms 12124 KB Output is correct
8 Correct 6 ms 12124 KB Output is correct
9 Correct 6 ms 12124 KB Output is correct
10 Correct 5 ms 12120 KB Output is correct
11 Correct 5 ms 12124 KB Output is correct
12 Correct 6 ms 12124 KB Output is correct
13 Correct 6 ms 12124 KB Output is correct
14 Correct 5 ms 12120 KB Output is correct
15 Correct 6 ms 12124 KB Output is correct
16 Correct 5 ms 12124 KB Output is correct
17 Correct 5 ms 12196 KB Output is correct
18 Correct 5 ms 12120 KB Output is correct
19 Correct 5 ms 12124 KB Output is correct
20 Correct 5 ms 12124 KB Output is correct
21 Correct 6 ms 12120 KB Output is correct
22 Correct 5 ms 12124 KB Output is correct
23 Correct 5 ms 12124 KB Output is correct
24 Correct 5 ms 12124 KB Output is correct
25 Correct 6 ms 12124 KB Output is correct
26 Correct 6 ms 12124 KB Output is correct
27 Correct 6 ms 12124 KB Output is correct
28 Correct 7 ms 12120 KB Output is correct
29 Correct 6 ms 12124 KB Output is correct
30 Correct 6 ms 12124 KB Output is correct
31 Correct 5 ms 12124 KB Output is correct
32 Correct 6 ms 12124 KB Output is correct
33 Correct 5 ms 12124 KB Output is correct
34 Correct 7 ms 12196 KB Output is correct
35 Correct 6 ms 12376 KB Output is correct
36 Correct 5 ms 12124 KB Output is correct
37 Correct 5 ms 12124 KB Output is correct
38 Correct 7 ms 12216 KB Output is correct
39 Correct 5 ms 12124 KB Output is correct
40 Correct 4 ms 12204 KB Output is correct
41 Correct 5 ms 12124 KB Output is correct
42 Correct 5 ms 12124 KB Output is correct
43 Correct 5 ms 12124 KB Output is correct
44 Correct 5 ms 12196 KB Output is correct
45 Correct 6 ms 12376 KB Output is correct
46 Correct 5 ms 12120 KB Output is correct
47 Correct 5 ms 12124 KB Output is correct
48 Correct 5 ms 12124 KB Output is correct
49 Correct 6 ms 12140 KB Output is correct
50 Correct 5 ms 12124 KB Output is correct
51 Correct 6 ms 12124 KB Output is correct
52 Correct 5 ms 12124 KB Output is correct
53 Correct 5 ms 12124 KB Output is correct
54 Correct 5 ms 12120 KB Output is correct
55 Correct 5 ms 12124 KB Output is correct
56 Correct 5 ms 12124 KB Output is correct
57 Correct 5 ms 12120 KB Output is correct
58 Correct 5 ms 12124 KB Output is correct
59 Correct 166 ms 37312 KB Output is correct
60 Correct 192 ms 40096 KB Output is correct
61 Correct 5 ms 12124 KB Output is correct
62 Correct 5 ms 12124 KB Output is correct
63 Correct 133 ms 34692 KB Output is correct
64 Correct 6 ms 12636 KB Output is correct
65 Correct 12 ms 13912 KB Output is correct
66 Correct 65 ms 27984 KB Output is correct
67 Correct 264 ms 47096 KB Output is correct
68 Correct 249 ms 47952 KB Output is correct
69 Correct 9 ms 13148 KB Output is correct
70 Correct 48 ms 21960 KB Output is correct
71 Correct 179 ms 43976 KB Output is correct
72 Correct 169 ms 42520 KB Output is correct
73 Correct 54 ms 19412 KB Output is correct
74 Correct 213 ms 38656 KB Output is correct
75 Correct 18 ms 15448 KB Output is correct
76 Correct 184 ms 43464 KB Output is correct
77 Correct 161 ms 43556 KB Output is correct
78 Correct 21 ms 15708 KB Output is correct
79 Correct 250 ms 45136 KB Output is correct
80 Correct 6 ms 12376 KB Output is correct
81 Correct 54 ms 21872 KB Output is correct
82 Correct 186 ms 41136 KB Output is correct
83 Correct 199 ms 38736 KB Output is correct
84 Correct 228 ms 38704 KB Output is correct
85 Correct 223 ms 38616 KB Output is correct
86 Correct 238 ms 40012 KB Output is correct
87 Correct 190 ms 40000 KB Output is correct