oj.uz

Submission #1008712

# Submission time Handle Problem Language Result Execution time Memory
1008712 2024-06-26T16:55:53 Z ByeWorld Network (BOI15_net) C++14
0 / 100
 0 ms 348 KB 
#include <bits/stdc++.h>
#pragma GCC optimize("O3", "unroll-loops")
#define ll long long
#define int long long
#define pb push_back
#define fi first
#define se second
#define lf (id<<1)
#define rg ((id<<1)|1)
#define md ((l+r)>>1)
#define ld long double
using namespace std;
typedef pair<int,int> pii;
typedef pair<pii, int> ipii;
const int MAXN = 3e3+10;
const int INF = 1e18+10;
const int LOG = 19;
const int MOD = 1e9+7;
const int SQRT = 450;
const vector<int> NOL = {};
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
const vector<int> dx = {1, -1, 0, 0};
const vector<int> dy = {0, 0, 1, -1};

int n;
vector <int> adj[MAXN];
vector <pii> ans;
set <pii> s;
int root, cnt, deg[MAXN];
vector <int> leaf[MAXN];

void dfs(int nw, int par){
	if(adj[nw].size()==1) leaf[cnt].pb(nw);
	for(auto nx : adj[nw]){
		if(nx==par) continue;
		dfs(nx, nw);
	}
}
signed main(){
	// ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
	cin >> n;
	for(int i=1; i<=n-1; i++){
		int x, y; cin >> x >> y;
		adj[x].pb(y); adj[y].pb(x);
	}
	int LE = 0;
	for(int i=1; i<=n; i++){
		if(adj[i].size()!=1) root = i;
		else LE++;
	}

	for(auto nx : adj[root]){ ++cnt; dfs(nx, root); } 
	for(int i=1; i<=cnt; i++){ 
		deg[i] = leaf[i].size(); s.insert({leaf[i].size(), i});
	}
	int las = 1;
	// cout << root << "\n";
	while(ans.size() != LE/2){
		int fr = (*(s.begin())).se, en = (*(--s.end())).se;
		// cout << fr << ' ' << en << " fr\n";
		s.erase(s.begin());
		if(fr != en) s.erase(--s.end()); 
		int l = leaf[fr].back(); leaf[fr].pop_back(); deg[fr]--;
		int r = leaf[en].back(); leaf[en].pop_back(); deg[en]--;
		las = r;
		ans.pb({l, r});
		if(deg[fr] != 0) s.insert({deg[fr], fr});
		if(fr != en) 
			if(deg[en] != 0) s.insert({deg[en], en});
	}
	if(LE%2){
		int l = leaf[(*(s.begin())).se].back();
		ans.pb({l, las});
	}
	cout << ans.size() << '\n';
	for(auto in : ans) cout << in.fi << ' ' << in.se << '\n';
}

Compilation message

net.cpp: In function 'int main()':
net.cpp:58:19: 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]
   58 |  while(ans.size() != LE/2){
      |        ~~~~~~~~~~~^~~~~~~

Subtask #1
0 / 18.0

# Verdict Execution time Memory Grader output
1 Correct 0 ms 348 KB Output is correct
2 Incorrect 0 ms 348 KB Breaking single line is causing network to disconnect.
3 Halted 0 ms 0 KB -

Subtask #2
0 / 45.0

# Verdict Execution time Memory Grader output
1 Correct 0 ms 348 KB Output is correct
2 Incorrect 0 ms 348 KB Breaking single line is causing network to disconnect.
3 Halted 0 ms 0 KB -

Subtask #3
0 / 37.0

# Verdict Execution time Memory Grader output
1 Correct 0 ms 348 KB Output is correct
2 Incorrect 0 ms 348 KB Breaking single line is causing network to disconnect.
3 Halted 0 ms 0 KB -