oj.uz

Submission #902742

# Submission time Handle Problem Language Result Execution time Memory
902742 2024-01-11T01:51:40 Z aqxa Network (BOI15_net) C++17
100 / 100
 710 ms 127668 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]) {
				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 0 ms 492 KB Output is correct
2 Correct 1 ms 344 KB Output is correct
3 Correct 0 ms 348 KB Output is correct
4 Correct 0 ms 348 KB Output is correct
5 Correct 1 ms 348 KB Output is correct
6 Correct 0 ms 348 KB Output is correct
7 Correct 0 ms 348 KB Output is correct
8 Correct 1 ms 348 KB Output is correct
9 Correct 0 ms 344 KB Output is correct
10 Correct 1 ms 356 KB Output is correct
11 Correct 1 ms 348 KB Output is correct
12 Correct 1 ms 348 KB Output is correct
13 Correct 1 ms 348 KB Output is correct
14 Correct 0 ms 352 KB Output is correct
15 Correct 0 ms 360 KB Output is correct
16 Correct 0 ms 360 KB Output is correct
17 Correct 0 ms 360 KB Output is correct
18 Correct 0 ms 360 KB Output is correct
19 Correct 0 ms 360 KB Output is correct
20 Correct 0 ms 360 KB Output is correct

Subtask #2
45.0 / 45.0

# Verdict Execution time Memory Grader output
1 Correct 0 ms 492 KB Output is correct
2 Correct 1 ms 344 KB Output is correct
3 Correct 0 ms 348 KB Output is correct
4 Correct 0 ms 348 KB Output is correct
5 Correct 1 ms 348 KB Output is correct
6 Correct 0 ms 348 KB Output is correct
7 Correct 0 ms 348 KB Output is correct
8 Correct 1 ms 348 KB Output is correct
9 Correct 0 ms 344 KB Output is correct
10 Correct 1 ms 356 KB Output is correct
11 Correct 1 ms 348 KB Output is correct
12 Correct 1 ms 348 KB Output is correct
13 Correct 1 ms 348 KB Output is correct
14 Correct 0 ms 352 KB Output is correct
15 Correct 0 ms 360 KB Output is correct
16 Correct 0 ms 360 KB Output is correct
17 Correct 0 ms 360 KB Output is correct
18 Correct 0 ms 360 KB Output is correct
19 Correct 0 ms 360 KB Output is correct
20 Correct 0 ms 360 KB Output is correct
21 Correct 0 ms 348 KB Output is correct
22 Correct 1 ms 1112 KB Output is correct
23 Correct 1 ms 856 KB Output is correct
24 Correct 1 ms 856 KB Output is correct
25 Correct 2 ms 768 KB Output is correct
26 Correct 1 ms 604 KB Output is correct
27 Correct 1 ms 604 KB Output is correct
28 Correct 1 ms 604 KB Output is correct
29 Correct 1 ms 604 KB Output is correct
30 Correct 0 ms 348 KB Output is correct
31 Correct 1 ms 604 KB Output is correct
32 Correct 1 ms 348 KB Output is correct
33 Correct 1 ms 348 KB Output is correct
34 Correct 0 ms 348 KB Output is correct
35 Correct 1 ms 348 KB Output is correct
36 Correct 0 ms 348 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 348 KB Output is correct
41 Correct 0 ms 348 KB Output is correct
42 Correct 0 ms 348 KB Output is correct
43 Correct 1 ms 604 KB Output is correct
44 Correct 0 ms 344 KB Output is correct
45 Correct 1 ms 348 KB Output is correct
46 Correct 1 ms 604 KB Output is correct
47 Correct 0 ms 348 KB Output is correct
48 Correct 0 ms 348 KB Output is correct
49 Correct 1 ms 604 KB Output is correct
50 Correct 0 ms 348 KB Output is correct
51 Correct 0 ms 344 KB Output is correct
52 Correct 1 ms 348 KB Output is correct
53 Correct 1 ms 604 KB Output is correct
54 Correct 1 ms 348 KB Output is correct
55 Correct 1 ms 360 KB Output is correct
56 Correct 0 ms 360 KB Output is correct
57 Correct 1 ms 344 KB Output is correct
58 Correct 2 ms 860 KB Output is correct

Subtask #3
37.0 / 37.0

# Verdict Execution time Memory Grader output
1 Correct 0 ms 492 KB Output is correct
2 Correct 1 ms 344 KB Output is correct
3 Correct 0 ms 348 KB Output is correct
4 Correct 0 ms 348 KB Output is correct
5 Correct 1 ms 348 KB Output is correct
6 Correct 0 ms 348 KB Output is correct
7 Correct 0 ms 348 KB Output is correct
8 Correct 1 ms 348 KB Output is correct
9 Correct 0 ms 344 KB Output is correct
10 Correct 1 ms 356 KB Output is correct
11 Correct 1 ms 348 KB Output is correct
12 Correct 1 ms 348 KB Output is correct
13 Correct 1 ms 348 KB Output is correct
14 Correct 0 ms 352 KB Output is correct
15 Correct 0 ms 360 KB Output is correct
16 Correct 0 ms 360 KB Output is correct
17 Correct 0 ms 360 KB Output is correct
18 Correct 0 ms 360 KB Output is correct
19 Correct 0 ms 360 KB Output is correct
20 Correct 0 ms 360 KB Output is correct
21 Correct 0 ms 348 KB Output is correct
22 Correct 1 ms 1112 KB Output is correct
23 Correct 1 ms 856 KB Output is correct
24 Correct 1 ms 856 KB Output is correct
25 Correct 2 ms 768 KB Output is correct
26 Correct 1 ms 604 KB Output is correct
27 Correct 1 ms 604 KB Output is correct
28 Correct 1 ms 604 KB Output is correct
29 Correct 1 ms 604 KB Output is correct
30 Correct 0 ms 348 KB Output is correct
31 Correct 1 ms 604 KB Output is correct
32 Correct 1 ms 348 KB Output is correct
33 Correct 1 ms 348 KB Output is correct
34 Correct 0 ms 348 KB Output is correct
35 Correct 1 ms 348 KB Output is correct
36 Correct 0 ms 348 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 348 KB Output is correct
41 Correct 0 ms 348 KB Output is correct
42 Correct 0 ms 348 KB Output is correct
43 Correct 1 ms 604 KB Output is correct
44 Correct 0 ms 344 KB Output is correct
45 Correct 1 ms 348 KB Output is correct
46 Correct 1 ms 604 KB Output is correct
47 Correct 0 ms 348 KB Output is correct
48 Correct 0 ms 348 KB Output is correct
49 Correct 1 ms 604 KB Output is correct
50 Correct 0 ms 348 KB Output is correct
51 Correct 0 ms 344 KB Output is correct
52 Correct 1 ms 348 KB Output is correct
53 Correct 1 ms 604 KB Output is correct
54 Correct 1 ms 348 KB Output is correct
55 Correct 1 ms 360 KB Output is correct
56 Correct 0 ms 360 KB Output is correct
57 Correct 1 ms 344 KB Output is correct
58 Correct 2 ms 860 KB Output is correct
59 Correct 472 ms 98888 KB Output is correct
60 Correct 646 ms 109708 KB Output is correct
61 Correct 0 ms 348 KB Output is correct
62 Correct 0 ms 348 KB Output is correct
63 Correct 412 ms 89832 KB Output is correct
64 Correct 2 ms 1372 KB Output is correct
65 Correct 11 ms 4992 KB Output is correct
66 Correct 156 ms 35288 KB Output is correct
67 Correct 509 ms 98772 KB Output is correct
68 Correct 710 ms 100940 KB Output is correct
69 Correct 10 ms 3416 KB Output is correct
70 Correct 142 ms 35564 KB Output is correct
71 Correct 415 ms 121404 KB Output is correct
72 Correct 438 ms 124256 KB Output is correct
73 Correct 148 ms 28944 KB Output is correct
74 Correct 614 ms 111016 KB Output is correct
75 Correct 38 ms 13392 KB Output is correct
76 Correct 432 ms 126756 KB Output is correct
77 Correct 422 ms 127668 KB Output is correct
78 Correct 42 ms 11356 KB Output is correct
79 Correct 492 ms 103296 KB Output is correct
80 Correct 4 ms 1116 KB Output is correct
81 Correct 147 ms 37980 KB Output is correct
82 Correct 530 ms 119368 KB Output is correct
83 Correct 587 ms 111180 KB Output is correct
84 Correct 602 ms 111188 KB Output is correct
85 Correct 616 ms 111032 KB Output is correct
86 Correct 615 ms 116308 KB Output is correct
87 Correct 596 ms 116428 KB Output is correct