oj.uz

Submission #902741

# Submission time Handle Problem Language Result Execution time Memory
902741 2024-01-11T01:48:51 Z aqxa Network (BOI15_net) C++17
63 / 100
 728 ms 127952 KB 
#include <bits/stdc++.h>
using namespace std;
 
#define ll long long
 
// works? 
struct graph {
    vector<vector<int>> adj;
    int n;
 
    graph() {} 
    graph(int _n) : n(_n) {
        adj.resize(n);
    }
 
    inline void add(int x, int y) {
        adj[x].push_back(y); 
        adj[y].push_back(x); 
    }
};
struct lca_graph : graph {
    using graph::adj;
    using graph::n; 
    vector<vector<int>> par; 
    vector<int> lev, path; 
    int lv = 0, lg; 
   	lca_graph(int _n) : graph(_n) {
        lg = __lg(n) + 1; 
        par = vector<vector<int>>(n, vector<int>(lg, -1)); 
        lev = vector<int>(n, 0); 
    }
    void make_lca(int x, int p) {
        path.push_back(x);
        lv++;
        lev[x] = lv;
 
        for (int i = 0; (1<<i) < path.size(); ++i) {
            par[x][i] = path[path.size()-1-(1<<i)];
        }
 
        for (auto u: adj[x]) {
            if (u != p) {
                make_lca(u, x);
            }
        }
        lv--;
        path.pop_back();
    }
    int ka(int u, int k) {
        if (k > lev[u] - 1) return 0; 
        while (k > 0) {
            int clg = (int) __lg(k);  
            k -= (1 << clg);
            u = par[u][clg];
        }
        return u;
    }
    int lca(int u, int v) {
        int du = lev[u], dv = lev[v];
        if (du < dv) {
            v = ka(v, dv - du);
            dv = du;
        } else if (du > dv) {
            u = ka(u, du - dv);
            du = dv;
        }
 
        if (u == v) return u;
 
        for (int i = lg-1; i >= 0; --i) {
            if (par[u][i] != par[v][i]) {
                u = par[u][i];  
                v = par[v][i];
				assert(u != -1 && v != -1);
            }
        }
		assert(u != -1); 
        return par[u][0];
    }
};
 
int main() {
	ios_base::sync_with_stdio(false); 
	cin.tie(0); 

// int tt; 
// cin >> tt;
// while (tt--) {
	int n; 
	cin >> n;
	lca_graph g(n); 
	for (int i = 0; i < n - 1; ++i) {
		int x, y; 
		cin >> x >> y; 
		g.add(--x, --y); 
	}
	vector<int> leafs; 
	set<int> leaf; 
	for (int i = 0; i < n; ++i) {
		if ((int) g.adj[i].size() == 1) {
			leaf.insert(i); 
			leafs.push_back(i); 
		}
	}
	for (int i = 0; i < n; ++i) {
		if (leaf.find(i) == leaf.end()) {
			g.make_lca(i, -1); 
			break; 
		}
	}
 
 	if ((int) leafs.size() % 2) {
		int x = leafs.back(); 
		for (int i = 0; i < n; ++i) {
			if (i != x && i != g.adj[x][0] && leaf.find(i) == leaf.end()) {
				leafs.push_back(i); 
				break; 
			}
		}
	}

	vector<pair<int, int>> ans; 
	
	for (int i = 0; i + 1 < (int) leafs.size(); i += 2) {
		if (!ans.size()) {
			ans.push_back(make_pair(leafs[i], leafs[i + 1])); 
			continue; 
		}
		auto p = ans.back(); 
		ans.pop_back(); 
		vector<int> v = {p.first, p.second, leafs[i], leafs[i + 1]}; 
		int best = 0; 
		pair<int, int> c = {2 * n, 2 * n}; 
		for (int f = 1; f < 4; ++f) {
			int a = g.lca(v[0], v[f]), b; 
			for (int j = 1; j < 4; ++j) {
				for (int k = j + 1; k < 4; ++k) {
					if (j != f && k != f) {
						b = g.lca(v[j], v[k]); 
						// cout << "Good\n";
					}
				}
			}
			a = g.lev[a]; 
			b = g.lev[b]; 
			if (a > b) swap(a, b); 
			pair<int, int> cur = {a, b}; 
			if (cur < c) {
				best = f; 
				c = cur; 
			}
		}
		ans.push_back({v[0], v[best]}); 
		for (int j = 1; j < 4; ++j) {
			for (int k = j + 1; k < 4; ++k) {
				if (j != best && k != best) {
					ans.push_back({v[j], v[k]}); 
				}
			}
		}
	}
 
	cout << (int) ans.size() << "\n";
	for (auto [x, y]: ans) {
		cout << x + 1 << " " << y + 1 << "\n";
	}
// }
 
	return 0;
}

Compilation message

net.cpp: In member function 'void lca_graph::make_lca(int, int)':
net.cpp:37:32: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   37 |         for (int i = 0; (1<<i) < path.size(); ++i) {
      |                         ~~~~~~~^~~~~~~~~~~~~
net.cpp: In function 'int main()':
net.cpp:145:15: warning: 'b' may be used uninitialized in this function [-Wmaybe-uninitialized]
  145 |    b = g.lev[b];
      |               ^

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 348 KB Output is correct
3 Correct 0 ms 456 KB Output is correct
4 Correct 1 ms 344 KB Output is correct
5 Correct 1 ms 356 KB Output is correct
6 Correct 1 ms 352 KB Output is correct
7 Correct 0 ms 344 KB Output is correct
8 Correct 1 ms 360 KB Output is correct
9 Correct 0 ms 348 KB Output is correct
10 Correct 0 ms 356 KB Output is correct
11 Correct 0 ms 360 KB Output is correct
12 Correct 0 ms 360 KB Output is correct
13 Correct 0 ms 348 KB Output is correct
14 Correct 1 ms 348 KB Output is correct
15 Correct 1 ms 348 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 348 KB Output is correct
19 Correct 1 ms 348 KB Output is correct
20 Correct 1 ms 348 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 348 KB Output is correct
3 Correct 0 ms 456 KB Output is correct
4 Correct 1 ms 344 KB Output is correct
5 Correct 1 ms 356 KB Output is correct
6 Correct 1 ms 352 KB Output is correct
7 Correct 0 ms 344 KB Output is correct
8 Correct 1 ms 360 KB Output is correct
9 Correct 0 ms 348 KB Output is correct
10 Correct 0 ms 356 KB Output is correct
11 Correct 0 ms 360 KB Output is correct
12 Correct 0 ms 360 KB Output is correct
13 Correct 0 ms 348 KB Output is correct
14 Correct 1 ms 348 KB Output is correct
15 Correct 1 ms 348 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 348 KB Output is correct
19 Correct 1 ms 348 KB Output is correct
20 Correct 1 ms 348 KB Output is correct
21 Correct 0 ms 348 KB Output is correct
22 Correct 2 ms 908 KB Output is correct
23 Correct 2 ms 728 KB Output is correct
24 Correct 2 ms 860 KB Output is correct
25 Correct 1 ms 612 KB Output is correct
26 Correct 1 ms 612 KB Output is correct
27 Correct 2 ms 772 KB Output is correct
28 Correct 1 ms 704 KB Output is correct
29 Correct 1 ms 616 KB Output is correct
30 Correct 0 ms 352 KB Output is correct
31 Correct 2 ms 872 KB Output is correct
32 Correct 1 ms 360 KB Output is correct
33 Correct 0 ms 360 KB Output is correct
34 Correct 0 ms 352 KB Output is correct
35 Correct 0 ms 360 KB Output is correct
36 Correct 1 ms 360 KB Output is correct
37 Correct 1 ms 348 KB Output is correct
38 Correct 1 ms 604 KB Output is correct
39 Correct 1 ms 348 KB Output is correct
40 Correct 1 ms 356 KB Output is correct
41 Correct 1 ms 348 KB Output is correct
42 Correct 1 ms 348 KB Output is correct
43 Correct 1 ms 604 KB Output is correct
44 Correct 0 ms 356 KB Output is correct
45 Correct 1 ms 360 KB Output is correct
46 Correct 1 ms 616 KB Output is correct
47 Correct 0 ms 360 KB Output is correct
48 Correct 1 ms 360 KB Output is correct
49 Correct 2 ms 604 KB Output is correct
50 Correct 0 ms 348 KB Output is correct
51 Correct 0 ms 348 KB Output is correct
52 Correct 1 ms 348 KB Output is correct
53 Correct 1 ms 604 KB Output is correct
54 Correct 0 ms 348 KB Output is correct
55 Correct 1 ms 348 KB Output is correct
56 Correct 0 ms 348 KB Output is correct
57 Correct 1 ms 348 KB Output is correct
58 Correct 1 ms 868 KB Output is correct

Subtask #3
0 / 37.0

# Verdict Execution time Memory Grader output
1 Correct 1 ms 344 KB Output is correct
2 Correct 1 ms 348 KB Output is correct
3 Correct 0 ms 456 KB Output is correct
4 Correct 1 ms 344 KB Output is correct
5 Correct 1 ms 356 KB Output is correct
6 Correct 1 ms 352 KB Output is correct
7 Correct 0 ms 344 KB Output is correct
8 Correct 1 ms 360 KB Output is correct
9 Correct 0 ms 348 KB Output is correct
10 Correct 0 ms 356 KB Output is correct
11 Correct 0 ms 360 KB Output is correct
12 Correct 0 ms 360 KB Output is correct
13 Correct 0 ms 348 KB Output is correct
14 Correct 1 ms 348 KB Output is correct
15 Correct 1 ms 348 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 348 KB Output is correct
19 Correct 1 ms 348 KB Output is correct
20 Correct 1 ms 348 KB Output is correct
21 Correct 0 ms 348 KB Output is correct
22 Correct 2 ms 908 KB Output is correct
23 Correct 2 ms 728 KB Output is correct
24 Correct 2 ms 860 KB Output is correct
25 Correct 1 ms 612 KB Output is correct
26 Correct 1 ms 612 KB Output is correct
27 Correct 2 ms 772 KB Output is correct
28 Correct 1 ms 704 KB Output is correct
29 Correct 1 ms 616 KB Output is correct
30 Correct 0 ms 352 KB Output is correct
31 Correct 2 ms 872 KB Output is correct
32 Correct 1 ms 360 KB Output is correct
33 Correct 0 ms 360 KB Output is correct
34 Correct 0 ms 352 KB Output is correct
35 Correct 0 ms 360 KB Output is correct
36 Correct 1 ms 360 KB Output is correct
37 Correct 1 ms 348 KB Output is correct
38 Correct 1 ms 604 KB Output is correct
39 Correct 1 ms 348 KB Output is correct
40 Correct 1 ms 356 KB Output is correct
41 Correct 1 ms 348 KB Output is correct
42 Correct 1 ms 348 KB Output is correct
43 Correct 1 ms 604 KB Output is correct
44 Correct 0 ms 356 KB Output is correct
45 Correct 1 ms 360 KB Output is correct
46 Correct 1 ms 616 KB Output is correct
47 Correct 0 ms 360 KB Output is correct
48 Correct 1 ms 360 KB Output is correct
49 Correct 2 ms 604 KB Output is correct
50 Correct 0 ms 348 KB Output is correct
51 Correct 0 ms 348 KB Output is correct
52 Correct 1 ms 348 KB Output is correct
53 Correct 1 ms 604 KB Output is correct
54 Correct 0 ms 348 KB Output is correct
55 Correct 1 ms 348 KB Output is correct
56 Correct 0 ms 348 KB Output is correct
57 Correct 1 ms 348 KB Output is correct
58 Correct 1 ms 868 KB Output is correct
59 Correct 517 ms 104784 KB Output is correct
60 Correct 654 ms 116544 KB Output is correct
61 Correct 1 ms 348 KB Output is correct
62 Correct 0 ms 348 KB Output is correct
63 Correct 424 ms 95096 KB Output is correct
64 Correct 2 ms 1372 KB Output is correct
65 Correct 16 ms 5212 KB Output is correct
66 Correct 143 ms 37452 KB Output is correct
67 Correct 545 ms 105664 KB Output is correct
68 Correct 728 ms 107744 KB Output is correct
69 Correct 9 ms 3676 KB Output is correct
70 Correct 123 ms 37456 KB Output is correct
71 Incorrect 472 ms 127952 KB Invalid number of links.
72 Halted 0 ms 0 KB -