답안 #137092

#	제출 시각	아이디	문제	언어	결과	실행 시간	메모리
137092	2019-07-27T05:12:57 Z	silxikys	Network (BOI15_net)	C++14	100 / 100	1022 ms	62668 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) {
    if (hasBridge) return;
    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);
    srand(time(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;
    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:31:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for (int i = 0; i < adj[now].size(); i++) {
                     ~~^~~~~~~~~~~~~~~~~
net.cpp:29:10: warning: variable 'isArt' set but not used [-Wunused-but-set-variable]
     bool isArt = false;
          ^~~~~
net.cpp: In function 'int main()':
net.cpp:87:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         for (int i = 0; i < leafs.size(); i += 2, id++) {
                         ~~^~~~~~~~~~~~~~
net.cpp:96:31: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
             for (int i = 0; i < leafs.size(); i += 2, id++) {
                             ~~^~~~~~~~~~~~~~

Subtask #1
18.0 / 18.0

#	결과	실행 시간	메모리	Grader output
1	Correct	17 ms	16504 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	16 ms	16504 KB	Output is correct
6	Correct	20 ms	16504 KB	Output is correct
7	Correct	20 ms	16504 KB	Output is correct
8	Correct	21 ms	16504 KB	Output is correct
9	Correct	20 ms	16504 KB	Output is correct
10	Correct	21 ms	16508 KB	Output is correct
11	Correct	20 ms	16632 KB	Output is correct
12	Correct	16 ms	16504 KB	Output is correct
13	Correct	19 ms	16504 KB	Output is correct
14	Correct	21 ms	16504 KB	Output is correct
15	Correct	19 ms	16504 KB	Output is correct
16	Correct	16 ms	16504 KB	Output is correct
17	Correct	17 ms	16504 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	16504 KB	Output is correct

Subtask #2
45.0 / 45.0

#	결과	실행 시간	메모리	Grader output
1	Correct	17 ms	16504 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	16 ms	16504 KB	Output is correct
6	Correct	20 ms	16504 KB	Output is correct
7	Correct	20 ms	16504 KB	Output is correct
8	Correct	21 ms	16504 KB	Output is correct
9	Correct	20 ms	16504 KB	Output is correct
10	Correct	21 ms	16508 KB	Output is correct
11	Correct	20 ms	16632 KB	Output is correct
12	Correct	16 ms	16504 KB	Output is correct
13	Correct	19 ms	16504 KB	Output is correct
14	Correct	21 ms	16504 KB	Output is correct
15	Correct	19 ms	16504 KB	Output is correct
16	Correct	16 ms	16504 KB	Output is correct
17	Correct	17 ms	16504 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	16504 KB	Output is correct
21	Correct	17 ms	16504 KB	Output is correct
22	Correct	18 ms	16632 KB	Output is correct
23	Correct	17 ms	16604 KB	Output is correct
24	Correct	18 ms	16632 KB	Output is correct
25	Correct	20 ms	16760 KB	Output is correct
26	Correct	17 ms	16644 KB	Output is correct
27	Correct	22 ms	16760 KB	Output is correct
28	Correct	17 ms	16760 KB	Output is correct
29	Correct	17 ms	16732 KB	Output is correct
30	Correct	17 ms	16484 KB	Output is correct
31	Correct	19 ms	16760 KB	Output is correct
32	Correct	17 ms	16504 KB	Output is correct
33	Correct	20 ms	16504 KB	Output is correct
34	Correct	17 ms	16508 KB	Output is correct
35	Correct	17 ms	16504 KB	Output is correct
36	Correct	17 ms	16508 KB	Output is correct
37	Correct	17 ms	16632 KB	Output is correct
38	Correct	18 ms	16632 KB	Output is correct
39	Correct	16 ms	16504 KB	Output is correct
40	Correct	16 ms	16504 KB	Output is correct
41	Correct	16 ms	16476 KB	Output is correct
42	Correct	17 ms	16504 KB	Output is correct
43	Correct	17 ms	16512 KB	Output is correct
44	Correct	17 ms	16504 KB	Output is correct
45	Correct	17 ms	16504 KB	Output is correct
46	Correct	18 ms	16632 KB	Output is correct
47	Correct	17 ms	16532 KB	Output is correct
48	Correct	17 ms	16508 KB	Output is correct
49	Correct	17 ms	16632 KB	Output is correct
50	Correct	17 ms	16504 KB	Output is correct
51	Correct	17 ms	16504 KB	Output is correct
52	Correct	17 ms	16504 KB	Output is correct
53	Correct	17 ms	16504 KB	Output is correct
54	Correct	17 ms	16504 KB	Output is correct
55	Correct	29 ms	16504 KB	Output is correct
56	Correct	17 ms	16504 KB	Output is correct
57	Correct	17 ms	16504 KB	Output is correct
58	Correct	18 ms	16632 KB	Output is correct

Subtask #3
37.0 / 37.0

#	결과	실행 시간	메모리	Grader output
1	Correct	17 ms	16504 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	16 ms	16504 KB	Output is correct
6	Correct	20 ms	16504 KB	Output is correct
7	Correct	20 ms	16504 KB	Output is correct
8	Correct	21 ms	16504 KB	Output is correct
9	Correct	20 ms	16504 KB	Output is correct
10	Correct	21 ms	16508 KB	Output is correct
11	Correct	20 ms	16632 KB	Output is correct
12	Correct	16 ms	16504 KB	Output is correct
13	Correct	19 ms	16504 KB	Output is correct
14	Correct	21 ms	16504 KB	Output is correct
15	Correct	19 ms	16504 KB	Output is correct
16	Correct	16 ms	16504 KB	Output is correct
17	Correct	17 ms	16504 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	16504 KB	Output is correct
21	Correct	17 ms	16504 KB	Output is correct
22	Correct	18 ms	16632 KB	Output is correct
23	Correct	17 ms	16604 KB	Output is correct
24	Correct	18 ms	16632 KB	Output is correct
25	Correct	20 ms	16760 KB	Output is correct
26	Correct	17 ms	16644 KB	Output is correct
27	Correct	22 ms	16760 KB	Output is correct
28	Correct	17 ms	16760 KB	Output is correct
29	Correct	17 ms	16732 KB	Output is correct
30	Correct	17 ms	16484 KB	Output is correct
31	Correct	19 ms	16760 KB	Output is correct
32	Correct	17 ms	16504 KB	Output is correct
33	Correct	20 ms	16504 KB	Output is correct
34	Correct	17 ms	16508 KB	Output is correct
35	Correct	17 ms	16504 KB	Output is correct
36	Correct	17 ms	16508 KB	Output is correct
37	Correct	17 ms	16632 KB	Output is correct
38	Correct	18 ms	16632 KB	Output is correct
39	Correct	16 ms	16504 KB	Output is correct
40	Correct	16 ms	16504 KB	Output is correct
41	Correct	16 ms	16476 KB	Output is correct
42	Correct	17 ms	16504 KB	Output is correct
43	Correct	17 ms	16512 KB	Output is correct
44	Correct	17 ms	16504 KB	Output is correct
45	Correct	17 ms	16504 KB	Output is correct
46	Correct	18 ms	16632 KB	Output is correct
47	Correct	17 ms	16532 KB	Output is correct
48	Correct	17 ms	16508 KB	Output is correct
49	Correct	17 ms	16632 KB	Output is correct
50	Correct	17 ms	16504 KB	Output is correct
51	Correct	17 ms	16504 KB	Output is correct
52	Correct	17 ms	16504 KB	Output is correct
53	Correct	17 ms	16504 KB	Output is correct
54	Correct	17 ms	16504 KB	Output is correct
55	Correct	29 ms	16504 KB	Output is correct
56	Correct	17 ms	16504 KB	Output is correct
57	Correct	17 ms	16504 KB	Output is correct
58	Correct	18 ms	16632 KB	Output is correct
59	Correct	941 ms	60240 KB	Output is correct
60	Correct	736 ms	58368 KB	Output is correct
61	Correct	17 ms	16504 KB	Output is correct
62	Correct	17 ms	16504 KB	Output is correct
63	Correct	587 ms	51048 KB	Output is correct
64	Correct	19 ms	16888 KB	Output is correct
65	Correct	30 ms	18424 KB	Output is correct
66	Correct	215 ms	30308 KB	Output is correct
67	Correct	618 ms	62668 KB	Output is correct
68	Correct	624 ms	52320 KB	Output is correct
69	Correct	26 ms	17656 KB	Output is correct
70	Correct	150 ms	27752 KB	Output is correct
71	Correct	591 ms	48316 KB	Output is correct
72	Correct	639 ms	47452 KB	Output is correct
73	Correct	139 ms	28136 KB	Output is correct
74	Correct	689 ms	55388 KB	Output is correct
75	Correct	52 ms	20468 KB	Output is correct
76	Correct	633 ms	53660 KB	Output is correct
77	Correct	652 ms	47300 KB	Output is correct
78	Correct	50 ms	20596 KB	Output is correct
79	Correct	616 ms	56672 KB	Output is correct
80	Correct	19 ms	16760 KB	Output is correct
81	Correct	175 ms	27112 KB	Output is correct
82	Correct	659 ms	48120 KB	Output is correct
83	Correct	679 ms	54368 KB	Output is correct
84	Correct	1022 ms	54392 KB	Output is correct
85	Correct	700 ms	54436 KB	Output is correct
86	Correct	704 ms	57180 KB	Output is correct
87	Correct	713 ms	57316 KB	Output is correct

답안 #137092

Compilation message

Subtask #1 18.0 / 18.0

Subtask #2 45.0 / 45.0

Subtask #3 37.0 / 37.0

Subtask #1
18.0 / 18.0

Subtask #2
45.0 / 45.0

Subtask #3
37.0 / 37.0