oj.uz

답안 #869447

# 제출 시각 아이디 문제 언어 결과 실행 시간 메모리
869447 2023-11-04T11:20:50 Z LeThanhMinh Network (BOI15_net) C++14
100 / 100
 591 ms 102836 KB 
    // Problem: H. Hai đường đi
    // Contest: Codeforces - 2023 winter contest #41, Dalat winter training camp, round 1
    // URL: https://gspvh23.contest.codeforces.com/group/FIWwc7nF6c/contest/484130/problem/H
    // Memory Limit: 512 MB
    // Time Limit: 2250 ms
    // 
    // Powered by CP Editor (https://cpeditor.org)
     
    /*CP template version 3.0 - Laconic*/
     
    #include <bits/stdc++.h>
     
    #define ii pair<int, int>
    #define fs first
    #define sc second
     
    //use struct instead of pair<int, ii>
     
    #define int long long
     
    #define show(v) {for (auto i : v) cout << i << " "; cout << endl;}
    #define showlr(v, l, r) {for (int i = l; i <= r; i++) cout << v[i] << " "; cout << endl;}
    #define all(v) v.begin(), v.end()
    #define SUnique(v) {sort(all(v)); v.erase(unique(all(v)), v.end());}
    #define forlr(i, l, r) for (int i = l; i <= r; i++)
    #define forrl(i, r, l) for (int i = r; i >= l; i--)
     
    #pragma GCC Optimize("O2")
    #define endl "\n"
    #define precise(x) cout << fixed << setprecision(x);
     
    using namespace std;
     
    const int N = 5e5 + 100;
    const int MOD = 1e9 + 7;
    const int INF = 1e9;
    const int LOG = 25;
    const long long LINF = 1e15 + 100;
     
    const int dx[4] = {1, 0, -1, 0};
    const int dy[4] = {0, -1, 0, 1};
     
    ostream& operator << (ostream &os, ii a) {
        
        os << a.fs << ' ' << a.sc;
        return os;
        
    }
     
    int binPow(int a, int b, int m = LLONG_MAX) {
        
        int prod = 1;
        a %= m;
        
        while (b) {
            
            if (b & 1) prod = prod * a % m;
            a = a * a % m;
            b /= 2;
            
        }
        
        return prod;
        
    }
     
    void setIO(string s) {
        
        if (s.empty()) return;
        
        freopen((s + ".inp").c_str(), "r", stdin);
        freopen((s + ".out").c_str(), "w", stdout);
        
    }
     
    //Try Brute Force (maybe there is a pattern)
    //Try DP (Weird constraints (sum of all elements <= 10000), small constraints)
    //Try Graph (a pair of number, condition between elements)
    //Try Geometry (Same as graph, for coordinate)
     
    //Try switching between problem
    //Put down what you have on paper
    //IMPORTANT: WRITE DOWN THE FORMULA
     
    int n, m, q, k;
    int arr[N];
    vector<int> adj[N], adj1[N];
     
    int low[N], num[N], head[N], timeDfs;
    stack<int> st;
    int bccId[N], bcc;
     
    void tarjan(int u, int pre) {
        
        st.push(u);
        num[u] = low[u] = ++timeDfs;
         
        for (int v : adj[u]) {
            
            if (v == pre) continue;
            if (num[v]) {
                
                low[u] = min(low[u], num[v]);
                
            } else {
                
                tarjan(v, u);
                low[u] = min(low[u], low[v]);
     
            }
            
        }
        
        if (num[u] == low[u]) {
            
            bcc++;
            int tmp;
            head[bcc] = u;
            
            do {
                
                tmp = st.top();
                bccId[tmp] = bcc;
                st.pop();
                num[u] = INF;
                
            } while (tmp != u);
     
        }
        
    }
     
    vector<int> leaf;
     
    void dfs1(int u, int pre) {
    	
    	if (adj1[u].size() == 1) {
    		
    		leaf.push_back(u);
    		if (u != pre) return;
    		
    	}
    	
    	for (int v : adj1[u]) {
    		
    		if (v == pre) continue;
    		dfs1(v, u);
    		
    	}
    	
    }
     
    mt19937 rng(chrono::steady_clock().now().time_since_epoch().count());
     
    ii edges[N];
     
    void solve() {
    	
    	cin >> n;
    	forlr(i, 1, n) adj[i].clear(), adj1[i].clear();
    	leaf.clear();
    	fill(bccId + 1, bccId + n + 1, 0);
    	fill(low + 1, low + n + 1, 0);
    	fill(num + 1, num + n + 1, 0);
    	fill(head + 1, head + n + 1, 0);
    	timeDfs = 0;
    	bcc = 0;
    	while (st.size()) st.pop();
    	
    	forlr(i, 1, n - 1) {
    		
    		int u, v; cin >> u >> v;
    		edges[i] = {u, v};
    		adj[u].push_back(v);
    		adj[v].push_back(u);
    		
    	}
    	
    	tarjan(1, 1);
    		
    	forlr(i, 1, n - 1) {
    		
    		auto [u, v] = edges[i];			
    		int idU = bccId[u], idV = bccId[v];
    		if (idU == idV) continue;
    		adj1[idU].push_back(idV);
    		adj1[idV].push_back(idU);
    		
    	}
    	
    	forlr(i, 1, n) SUnique(adj1[i]);
    	
    	dfs1(1, 1);
    	
    	vector<ii> res;
    	
    	int sz = leaf.size();
    	if (sz == 2) {
    		
    		cout << 1 << endl;
    		cout << head[leaf[0]] << " " << head[leaf[1]] << endl;
    		return;
    		
    	}
    	
    	if (sz <= 1) {
    		
    		cout << 0 << endl;
    		return;
    		
    	}
    	
    	forlr(i, 0, (sz - 1) / 2) res.push_back({head[leaf[i]], head[leaf[i + sz / 2]]});
    	
    	cout << res.size() << endl;
      	assert(res.size() == (sz + 1) / 2);
    	for (ii i : res) cout << i << endl;
        
    }
     
    signed main() {
        
        ios_base::sync_with_stdio(0);
        cin.tie(0); cout.tie(0);    
        // setIO("biconnected");
        
        int T = 1;
        
        bool multiTest = 0;
        if (multiTest) cin >> T;
            
        while (T--) {
            
            solve();
        
        }
        
    }

Compilation message

net.cpp:28: warning: ignoring '#pragma GCC Optimize' [-Wunknown-pragmas]
   28 |     #pragma GCC Optimize("O2")
      | 
net.cpp: In function 'void solve()':
net.cpp:183:12: warning: structured bindings only available with '-std=c++17' or '-std=gnu++17'
  183 |       auto [u, v] = edges[i];
      |            ^
In file included from /usr/include/c++/10/cassert:44,
                 from /usr/include/x86_64-linux-gnu/c++/10/bits/stdc++.h:33,
                 from net.cpp:11:
net.cpp:216:26: warning: comparison of integer expressions of different signedness: 'std::vector<std::pair<long long int, long long int> >::size_type' {aka 'long unsigned int'} and 'long long int' [-Wsign-compare]
  216 |        assert(res.size() == (sz + 1) / 2);
      |               ~~~~~~~~~~~^~~~~~~~~~~~~~~
net.cpp: In function 'void setIO(std::string)':
net.cpp:71:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   71 |         freopen((s + ".inp").c_str(), "r", stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
net.cpp:72:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   72 |         freopen((s + ".out").c_str(), "w", stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Subtask #1
18.0 / 18.0

# 결과 실행 시간 메모리 Grader output
1 Correct 6 ms 33112 KB Output is correct
2 Correct 6 ms 33116 KB Output is correct
3 Correct 6 ms 33112 KB Output is correct
4 Correct 6 ms 33112 KB Output is correct
5 Correct 7 ms 33116 KB Output is correct
6 Correct 6 ms 33116 KB Output is correct
7 Correct 7 ms 33116 KB Output is correct
8 Correct 6 ms 33116 KB Output is correct
9 Correct 7 ms 33288 KB Output is correct
10 Correct 6 ms 33116 KB Output is correct
11 Correct 6 ms 33116 KB Output is correct
12 Correct 7 ms 33116 KB Output is correct
13 Correct 6 ms 33292 KB Output is correct
14 Correct 6 ms 33116 KB Output is correct
15 Correct 7 ms 33116 KB Output is correct
16 Correct 6 ms 33236 KB Output is correct
17 Correct 6 ms 33116 KB Output is correct
18 Correct 7 ms 33284 KB Output is correct
19 Correct 7 ms 33288 KB Output is correct
20 Correct 6 ms 33116 KB Output is correct

Subtask #2
45.0 / 45.0

# 결과 실행 시간 메모리 Grader output
1 Correct 6 ms 33112 KB Output is correct
2 Correct 6 ms 33116 KB Output is correct
3 Correct 6 ms 33112 KB Output is correct
4 Correct 6 ms 33112 KB Output is correct
5 Correct 7 ms 33116 KB Output is correct
6 Correct 6 ms 33116 KB Output is correct
7 Correct 7 ms 33116 KB Output is correct
8 Correct 6 ms 33116 KB Output is correct
9 Correct 7 ms 33288 KB Output is correct
10 Correct 6 ms 33116 KB Output is correct
11 Correct 6 ms 33116 KB Output is correct
12 Correct 7 ms 33116 KB Output is correct
13 Correct 6 ms 33292 KB Output is correct
14 Correct 6 ms 33116 KB Output is correct
15 Correct 7 ms 33116 KB Output is correct
16 Correct 6 ms 33236 KB Output is correct
17 Correct 6 ms 33116 KB Output is correct
18 Correct 7 ms 33284 KB Output is correct
19 Correct 7 ms 33288 KB Output is correct
20 Correct 6 ms 33116 KB Output is correct
21 Correct 7 ms 33112 KB Output is correct
22 Correct 7 ms 33372 KB Output is correct
23 Correct 7 ms 33620 KB Output is correct
24 Correct 7 ms 33372 KB Output is correct
25 Correct 7 ms 33492 KB Output is correct
26 Correct 7 ms 33368 KB Output is correct
27 Correct 8 ms 33496 KB Output is correct
28 Correct 7 ms 33372 KB Output is correct
29 Correct 7 ms 33372 KB Output is correct
30 Correct 6 ms 33116 KB Output is correct
31 Correct 7 ms 33356 KB Output is correct
32 Correct 6 ms 33228 KB Output is correct
33 Correct 6 ms 33116 KB Output is correct
34 Correct 7 ms 33112 KB Output is correct
35 Correct 6 ms 33116 KB Output is correct
36 Correct 10 ms 33112 KB Output is correct
37 Correct 6 ms 33372 KB Output is correct
38 Correct 7 ms 33372 KB Output is correct
39 Correct 7 ms 33116 KB Output is correct
40 Correct 6 ms 33112 KB Output is correct
41 Correct 6 ms 33116 KB Output is correct
42 Correct 7 ms 33116 KB Output is correct
43 Correct 7 ms 33372 KB Output is correct
44 Correct 6 ms 33116 KB Output is correct
45 Correct 6 ms 33236 KB Output is correct
46 Correct 7 ms 33372 KB Output is correct
47 Correct 7 ms 33116 KB Output is correct
48 Correct 8 ms 33208 KB Output is correct
49 Correct 7 ms 33372 KB Output is correct
50 Correct 7 ms 33112 KB Output is correct
51 Correct 7 ms 33116 KB Output is correct
52 Correct 7 ms 33116 KB Output is correct
53 Correct 8 ms 33368 KB Output is correct
54 Correct 6 ms 33116 KB Output is correct
55 Correct 6 ms 33112 KB Output is correct
56 Correct 7 ms 33116 KB Output is correct
57 Correct 6 ms 33372 KB Output is correct
58 Correct 8 ms 33372 KB Output is correct

Subtask #3
37.0 / 37.0

# 결과 실행 시간 메모리 Grader output
1 Correct 6 ms 33112 KB Output is correct
2 Correct 6 ms 33116 KB Output is correct
3 Correct 6 ms 33112 KB Output is correct
4 Correct 6 ms 33112 KB Output is correct
5 Correct 7 ms 33116 KB Output is correct
6 Correct 6 ms 33116 KB Output is correct
7 Correct 7 ms 33116 KB Output is correct
8 Correct 6 ms 33116 KB Output is correct
9 Correct 7 ms 33288 KB Output is correct
10 Correct 6 ms 33116 KB Output is correct
11 Correct 6 ms 33116 KB Output is correct
12 Correct 7 ms 33116 KB Output is correct
13 Correct 6 ms 33292 KB Output is correct
14 Correct 6 ms 33116 KB Output is correct
15 Correct 7 ms 33116 KB Output is correct
16 Correct 6 ms 33236 KB Output is correct
17 Correct 6 ms 33116 KB Output is correct
18 Correct 7 ms 33284 KB Output is correct
19 Correct 7 ms 33288 KB Output is correct
20 Correct 6 ms 33116 KB Output is correct
21 Correct 7 ms 33112 KB Output is correct
22 Correct 7 ms 33372 KB Output is correct
23 Correct 7 ms 33620 KB Output is correct
24 Correct 7 ms 33372 KB Output is correct
25 Correct 7 ms 33492 KB Output is correct
26 Correct 7 ms 33368 KB Output is correct
27 Correct 8 ms 33496 KB Output is correct
28 Correct 7 ms 33372 KB Output is correct
29 Correct 7 ms 33372 KB Output is correct
30 Correct 6 ms 33116 KB Output is correct
31 Correct 7 ms 33356 KB Output is correct
32 Correct 6 ms 33228 KB Output is correct
33 Correct 6 ms 33116 KB Output is correct
34 Correct 7 ms 33112 KB Output is correct
35 Correct 6 ms 33116 KB Output is correct
36 Correct 10 ms 33112 KB Output is correct
37 Correct 6 ms 33372 KB Output is correct
38 Correct 7 ms 33372 KB Output is correct
39 Correct 7 ms 33116 KB Output is correct
40 Correct 6 ms 33112 KB Output is correct
41 Correct 6 ms 33116 KB Output is correct
42 Correct 7 ms 33116 KB Output is correct
43 Correct 7 ms 33372 KB Output is correct
44 Correct 6 ms 33116 KB Output is correct
45 Correct 6 ms 33236 KB Output is correct
46 Correct 7 ms 33372 KB Output is correct
47 Correct 7 ms 33116 KB Output is correct
48 Correct 8 ms 33208 KB Output is correct
49 Correct 7 ms 33372 KB Output is correct
50 Correct 7 ms 33112 KB Output is correct
51 Correct 7 ms 33116 KB Output is correct
52 Correct 7 ms 33116 KB Output is correct
53 Correct 8 ms 33368 KB Output is correct
54 Correct 6 ms 33116 KB Output is correct
55 Correct 6 ms 33112 KB Output is correct
56 Correct 7 ms 33116 KB Output is correct
57 Correct 6 ms 33372 KB Output is correct
58 Correct 8 ms 33372 KB Output is correct
59 Correct 389 ms 92540 KB Output is correct
60 Correct 495 ms 99256 KB Output is correct
61 Correct 6 ms 33112 KB Output is correct
62 Correct 7 ms 33116 KB Output is correct
63 Correct 320 ms 88772 KB Output is correct
64 Correct 8 ms 33880 KB Output is correct
65 Correct 17 ms 38492 KB Output is correct
66 Correct 112 ms 70352 KB Output is correct
67 Correct 588 ms 102604 KB Output is correct
68 Correct 577 ms 102836 KB Output is correct
69 Correct 12 ms 36952 KB Output is correct
70 Correct 81 ms 63184 KB Output is correct
71 Correct 248 ms 98356 KB Output is correct
72 Correct 281 ms 98104 KB Output is correct
73 Correct 80 ms 54124 KB Output is correct
74 Correct 535 ms 91200 KB Output is correct
75 Correct 33 ms 41048 KB Output is correct
76 Correct 273 ms 97572 KB Output is correct
77 Correct 243 ms 98220 KB Output is correct
78 Correct 32 ms 40788 KB Output is correct
79 Correct 591 ms 96992 KB Output is correct
80 Correct 8 ms 33628 KB Output is correct
81 Correct 99 ms 61500 KB Output is correct
82 Correct 407 ms 95200 KB Output is correct
83 Correct 488 ms 90880 KB Output is correct
84 Correct 504 ms 90872 KB Output is correct
85 Correct 546 ms 90880 KB Output is correct
86 Correct 566 ms 97432 KB Output is correct
87 Correct 488 ms 97828 KB Output is correct