oj.uz

Submission #137090

# Submission time Handle Problem Language Result Execution time Memory
137090 2019-07-27T05:08:18 Z silxikys Network (BOI15_net) C++14
100 / 100
 852 ms 68180 KB 
#include <bits/stdc++.h>
using namespace std;
using ll = long long;

const int maxn = 5e5+5;
int n;
int deg[maxn];
int subtree[maxn];

int pre[maxn];
int low[maxn];
bool v[maxn];

int point = 0;

struct Edge
{
    int to, id;
};
vector<Edge> adj[maxn];

bool hasBridge = false;

void go(int now, int fromID) {
    pre[now] = point++;
    v[now] = true;
    low[now] = pre[now];
    bool isArt = false;
    int childCnt = 0;
    for (int i = 0; i < adj[now].size(); i++) {
        if (adj[now][i].id == fromID) continue;
        int to = adj[now][i].to;
        if (v[to]) {
            //to must be an ancestor of now
            low[now] = min(low[now],pre[to]);
        }
        else {
            //bold edge going downwards
            go(to,adj[now][i].id);
            childCnt++;
            low[now] = min(low[now],low[to]);
            if (low[to] >= pre[now]) {
                isArt = true;
            }
            if (pre[now] < low[to]) {
                hasBridge = true;
            }
        }
    }
    if (fromID == -1) {
        isArt = childCnt != 1;
    }
}

int main()
{
    ios_base::sync_with_stdio(false); cin.tie(NULL);
    cin >> n;
    vector<pair<int,int>> edges;
    for (int i = 0; i < n - 1; i++) {
        int a, b; cin >> a >> b;
        ++deg[a];
        ++deg[b];
        edges.push_back({a,b});
    }
    vector<int> leafs;
    int start = 1;
    for (int i = 1; i <= n; i++) {
        if (deg[i] == 1) leafs.push_back(i);
    }
    while (true) {
        point = 0;
        memset(v,false,sizeof v);
        memset(pre,0,sizeof pre);
        memset(low,false,sizeof low);
        hasBridge = false;
        random_shuffle(leafs.begin(),leafs.end());
        int id = 0;
        for (int i = 1; i <= n; i++) {
            adj[i].clear();
        }
        for (int i = 0; i < n - 1; i++, id++) {
            adj[edges[i].second].push_back({edges[i].first,id});
            adj[edges[i].first].push_back({edges[i].second,id});
        }
        for (int i = 0; i < leafs.size(); i += 2, id++) {
            int nxt = leafs[(i+1)%leafs.size()];
            adj[leafs[i]].push_back({nxt,id});
            adj[nxt].push_back({leafs[i],id});
        }
        go(1,-1);
        if (!hasBridge) {
            //output
            cout << ((leafs.size()+1)/2) << '\n';
            for (int i = 0; i < leafs.size(); i += 2, id++) {
                int nxt = leafs[(i+1)%leafs.size()];
                cout << leafs[i] << ' ' << nxt << '\n';
            }
            return 0;
        }
    }
}

Compilation message

net.cpp: In function 'void go(int, int)':
net.cpp:30:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for (int i = 0; i < adj[now].size(); i++) {
                     ~~^~~~~~~~~~~~~~~~~
net.cpp:28:10: warning: variable 'isArt' set but not used [-Wunused-but-set-variable]
     bool isArt = false;
          ^~~~~
net.cpp: In function 'int main()':
net.cpp:86:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         for (int i = 0; i < leafs.size(); i += 2, id++) {
                         ~~^~~~~~~~~~~~~~
net.cpp:95:31: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
             for (int i = 0; i < leafs.size(); i += 2, id++) {
                             ~~^~~~~~~~~~~~~~
net.cpp:67:9: warning: unused variable 'start' [-Wunused-variable]
     int start = 1;
         ^~~~~

Subtask #1
18.0 / 18.0

# Verdict Execution time Memory Grader output
1 Correct 17 ms 16632 KB Output is correct
2 Correct 17 ms 16504 KB Output is correct
3 Correct 17 ms 16504 KB Output is correct
4 Correct 17 ms 16504 KB Output is correct
5 Correct 17 ms 16504 KB Output is correct
6 Correct 17 ms 16504 KB Output is correct
7 Correct 16 ms 16504 KB Output is correct
8 Correct 17 ms 16504 KB Output is correct
9 Correct 17 ms 16504 KB Output is correct
10 Correct 17 ms 16504 KB Output is correct
11 Correct 17 ms 16504 KB Output is correct
12 Correct 17 ms 16504 KB Output is correct
13 Correct 17 ms 16604 KB Output is correct
14 Correct 18 ms 16504 KB Output is correct
15 Correct 18 ms 16504 KB Output is correct
16 Correct 17 ms 16504 KB Output is correct
17 Correct 17 ms 16508 KB Output is correct
18 Correct 17 ms 16504 KB Output is correct
19 Correct 17 ms 16504 KB Output is correct
20 Correct 17 ms 16632 KB Output is correct

Subtask #2
45.0 / 45.0

# Verdict Execution time Memory Grader output
1 Correct 17 ms 16632 KB Output is correct
2 Correct 17 ms 16504 KB Output is correct
3 Correct 17 ms 16504 KB Output is correct
4 Correct 17 ms 16504 KB Output is correct
5 Correct 17 ms 16504 KB Output is correct
6 Correct 17 ms 16504 KB Output is correct
7 Correct 16 ms 16504 KB Output is correct
8 Correct 17 ms 16504 KB Output is correct
9 Correct 17 ms 16504 KB Output is correct
10 Correct 17 ms 16504 KB Output is correct
11 Correct 17 ms 16504 KB Output is correct
12 Correct 17 ms 16504 KB Output is correct
13 Correct 17 ms 16604 KB Output is correct
14 Correct 18 ms 16504 KB Output is correct
15 Correct 18 ms 16504 KB Output is correct
16 Correct 17 ms 16504 KB Output is correct
17 Correct 17 ms 16508 KB Output is correct
18 Correct 17 ms 16504 KB Output is correct
19 Correct 17 ms 16504 KB Output is correct
20 Correct 17 ms 16632 KB Output is correct
21 Correct 17 ms 16504 KB Output is correct
22 Correct 18 ms 16632 KB Output is correct
23 Correct 18 ms 16760 KB Output is correct
24 Correct 18 ms 16632 KB Output is correct
25 Correct 19 ms 16636 KB Output is correct
26 Correct 17 ms 16632 KB Output is correct
27 Correct 18 ms 16760 KB Output is correct
28 Correct 18 ms 16632 KB Output is correct
29 Correct 18 ms 16632 KB Output is correct
30 Correct 18 ms 16504 KB Output is correct
31 Correct 18 ms 16632 KB Output is correct
32 Correct 16 ms 16504 KB Output is correct
33 Correct 17 ms 16504 KB Output is correct
34 Correct 16 ms 16504 KB Output is correct
35 Correct 17 ms 16504 KB Output is correct
36 Correct 17 ms 16504 KB Output is correct
37 Correct 17 ms 16632 KB Output is correct
38 Correct 17 ms 16632 KB Output is correct
39 Correct 17 ms 16508 KB Output is correct
40 Correct 17 ms 16632 KB Output is correct
41 Correct 17 ms 16504 KB Output is correct
42 Correct 17 ms 16504 KB Output is correct
43 Correct 17 ms 16632 KB Output is correct
44 Correct 18 ms 16548 KB Output is correct
45 Correct 17 ms 16504 KB Output is correct
46 Correct 18 ms 16608 KB Output is correct
47 Correct 17 ms 16504 KB Output is correct
48 Correct 17 ms 16504 KB Output is correct
49 Correct 18 ms 16504 KB Output is correct
50 Correct 17 ms 16504 KB Output is correct
51 Correct 16 ms 16504 KB Output is correct
52 Correct 17 ms 16504 KB Output is correct
53 Correct 17 ms 16604 KB Output is correct
54 Correct 17 ms 16504 KB Output is correct
55 Correct 17 ms 16504 KB Output is correct
56 Correct 16 ms 16492 KB Output is correct
57 Correct 17 ms 16548 KB Output is correct
58 Correct 18 ms 16632 KB Output is correct

Subtask #3
37.0 / 37.0

# Verdict Execution time Memory Grader output
1 Correct 17 ms 16632 KB Output is correct
2 Correct 17 ms 16504 KB Output is correct
3 Correct 17 ms 16504 KB Output is correct
4 Correct 17 ms 16504 KB Output is correct
5 Correct 17 ms 16504 KB Output is correct
6 Correct 17 ms 16504 KB Output is correct
7 Correct 16 ms 16504 KB Output is correct
8 Correct 17 ms 16504 KB Output is correct
9 Correct 17 ms 16504 KB Output is correct
10 Correct 17 ms 16504 KB Output is correct
11 Correct 17 ms 16504 KB Output is correct
12 Correct 17 ms 16504 KB Output is correct
13 Correct 17 ms 16604 KB Output is correct
14 Correct 18 ms 16504 KB Output is correct
15 Correct 18 ms 16504 KB Output is correct
16 Correct 17 ms 16504 KB Output is correct
17 Correct 17 ms 16508 KB Output is correct
18 Correct 17 ms 16504 KB Output is correct
19 Correct 17 ms 16504 KB Output is correct
20 Correct 17 ms 16632 KB Output is correct
21 Correct 17 ms 16504 KB Output is correct
22 Correct 18 ms 16632 KB Output is correct
23 Correct 18 ms 16760 KB Output is correct
24 Correct 18 ms 16632 KB Output is correct
25 Correct 19 ms 16636 KB Output is correct
26 Correct 17 ms 16632 KB Output is correct
27 Correct 18 ms 16760 KB Output is correct
28 Correct 18 ms 16632 KB Output is correct
29 Correct 18 ms 16632 KB Output is correct
30 Correct 18 ms 16504 KB Output is correct
31 Correct 18 ms 16632 KB Output is correct
32 Correct 16 ms 16504 KB Output is correct
33 Correct 17 ms 16504 KB Output is correct
34 Correct 16 ms 16504 KB Output is correct
35 Correct 17 ms 16504 KB Output is correct
36 Correct 17 ms 16504 KB Output is correct
37 Correct 17 ms 16632 KB Output is correct
38 Correct 17 ms 16632 KB Output is correct
39 Correct 17 ms 16508 KB Output is correct
40 Correct 17 ms 16632 KB Output is correct
41 Correct 17 ms 16504 KB Output is correct
42 Correct 17 ms 16504 KB Output is correct
43 Correct 17 ms 16632 KB Output is correct
44 Correct 18 ms 16548 KB Output is correct
45 Correct 17 ms 16504 KB Output is correct
46 Correct 18 ms 16608 KB Output is correct
47 Correct 17 ms 16504 KB Output is correct
48 Correct 17 ms 16504 KB Output is correct
49 Correct 18 ms 16504 KB Output is correct
50 Correct 17 ms 16504 KB Output is correct
51 Correct 16 ms 16504 KB Output is correct
52 Correct 17 ms 16504 KB Output is correct
53 Correct 17 ms 16604 KB Output is correct
54 Correct 17 ms 16504 KB Output is correct
55 Correct 17 ms 16504 KB Output is correct
56 Correct 16 ms 16492 KB Output is correct
57 Correct 17 ms 16548 KB Output is correct
58 Correct 18 ms 16632 KB Output is correct
59 Correct 682 ms 60112 KB Output is correct
60 Correct 718 ms 63968 KB Output is correct
61 Correct 17 ms 16504 KB Output is correct
62 Correct 17 ms 16508 KB Output is correct
63 Correct 586 ms 55264 KB Output is correct
64 Correct 23 ms 16888 KB Output is correct
65 Correct 34 ms 18424 KB Output is correct
66 Correct 180 ms 30960 KB Output is correct
67 Correct 623 ms 68180 KB Output is correct
68 Correct 689 ms 58008 KB Output is correct
69 Correct 29 ms 17528 KB Output is correct
70 Correct 224 ms 28724 KB Output is correct
71 Correct 602 ms 54092 KB Output is correct
72 Correct 589 ms 52740 KB Output is correct
73 Correct 203 ms 28796 KB Output is correct
74 Correct 701 ms 61152 KB Output is correct
75 Correct 52 ms 20468 KB Output is correct
76 Correct 627 ms 53644 KB Output is correct
77 Correct 674 ms 53860 KB Output is correct
78 Correct 52 ms 21188 KB Output is correct
79 Correct 641 ms 63324 KB Output is correct
80 Correct 19 ms 16844 KB Output is correct
81 Correct 180 ms 29268 KB Output is correct
82 Correct 715 ms 54332 KB Output is correct
83 Correct 852 ms 60972 KB Output is correct
84 Correct 702 ms 60912 KB Output is correct
85 Correct 691 ms 60992 KB Output is correct
86 Correct 741 ms 63804 KB Output is correct
87 Correct 753 ms 63684 KB Output is correct