Submission #378213

#	Time	Username	Problem	Language	Result	Execution time	Memory
378213		AriaH	Railway (BOI17_railway)	C++11	100 / 100	308 ms	125156 KiB

railway

/** I can do this all day **/

#pragma GCC optimize("O2")
#include <bits/stdc++.h>
using namespace std;

typedef long long                   ll;
typedef long double                 ld;
typedef pair<int,int>               pii;
typedef pair<ll,ll>                 pll;
#define all(x)                      (x).begin(),(x).end()
#define F                           first
#define S                           second
#define Mp                          make_pair
#define SZ(x)			    		(int)x.size()
#define fast_io                     ios::sync_with_stdio(false);cin.tie(0);cout.tie(0);
#define file_io                     freopen("in.txt" , "r+" , stdin) ; freopen("out.txt" , "w+" , stdout);

const int N = 1e6 + 10;
const ll mod = 1e9 + 7;
const ll mod2 = 998244353;
const ll inf = 8e18;
const int LOG = 22;

ll pw(ll a , ll b, ll M)  { return (!b ? 1 : (b & 1 ? (a * pw(a * a % M, b / 2, M)) % M : pw(a * a % M, b / 2, M))); }

int n, m, k, sz[N];

map < int, int > mp[N];

vector < pii > G[N];

vector < int > tot, add[N];

void dfs(int v, int last = 0)
{
	for(auto x : add[v])
	{
		mp[v][x] ++;
		if(mp[v][x] == sz[x])
		{
			mp[v].erase(mp[v].find(x));
		}
	}
	for(auto y : G[v])
	{
		int u = y.F, id = y.S;
		if(id == last) continue;
		dfs(u, id);
		if(SZ(mp[v]) < SZ(mp[u]))
		{
			mp[v].swap(mp[u]);
		}
		for(auto it = mp[u].begin(); it != mp[u].end(); it ++)
		{
			if(it->S == 0) continue;
			mp[v][it->F] += it->S;
			if(sz[it->F] == mp[v][it->F])
			{
				mp[v].erase(mp[v].find(it->F));
			}
		}
	}
	if(SZ(mp[v]) >= k)
	{
		tot.push_back(last);
	}
}

int main()
{
	scanf("%d%d%d", &n, &m, &k);
	for(int i = 1; i < n; i ++)
	{
		int a, b;
		scanf("%d%d", &a,&b);
		G[a].push_back(Mp(b, i));
		G[b].push_back(Mp(a, i));
	}
	for(int i = 1; i <= m; i ++)
	{
		scanf("%d", &sz[i]);
		for(int j = 1; j <= sz[i]; j ++)
		{
			int x;
			scanf("%d", &x);
			add[x].push_back(i);
		}
	}
	dfs(1);
	sort(all(tot));
	printf("%d\n", SZ(tot));
	for(auto x : tot) printf("%d ", x);
    return 0;
}

/** test corner cases(n = 1?) watch for overflow or minus indices **/

Compilation message (stderr)

railway.cpp: In function 'int main()':
railway.cpp:72:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   72 |  scanf("%d%d%d", &n, &m, &k);
      |  ~~~~~^~~~~~~~~~~~~~~~~~~~~~
railway.cpp:76:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   76 |   scanf("%d%d", &a,&b);
      |   ~~~~~^~~~~~~~~~~~~~~
railway.cpp:82:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   82 |   scanf("%d", &sz[i]);
      |   ~~~~~^~~~~~~~~~~~~~
railway.cpp:86:9: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   86 |    scanf("%d", &x);
      |    ~~~~~^~~~~~~~~~

• Subtask 1: 8 / 8
• Subtask 2: 15 / 15
• Subtask 3: 7 / 7
• Subtask 4: 29 / 29
• Subtask 5: 16 / 16
• Subtask 6: 25 / 25