Submission #378447

#	Time	Username	Problem	Language	Result	Execution time	Memory
378447		AriaH	Pipes (CEOI15_pipes)	C++11	50 / 100	1556 ms	65536 KiB

pipes

/** 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 = 1e5 + 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))); }

struct dsu
{
	int par[N];
	void init()
	{
		iota(par, par + N, 0);
	}
	int get(int x)
	{
		return (x == par[x]? x : par[x] = get(par[x]));
	}
	int unify(int v, int u)
	{
		v = get(v), u = get(u);
		if(v == u)
		{
			return 0;
		}
		par[u] = v;
		return 1;
	}
} A, B;

int n, m, H[N], Up[N];

vector < pii > G[N];

void dfs(int v, int last)
{
	Up[v] = H[v];
	for(auto y : G[v])
	{
		int u = y.F, id = y.S;
		if(id == last) continue;
		if(H[u])
		{
			Up[v] = min(Up[v], H[u]);
		}
		else
		{
			H[u] = H[v] + 1;
			dfs(u, id);
			if(Up[u] > H[v])
			{
				printf("%d %d\n", v, u);
			}
			Up[v] = min(Up[v], Up[u]);
		}
	}
}

int main()
{
	A.init(), B.init();
	scanf("%d%d", &n, &m);
	int ptr = 0;
	for(int i = 1; i <= m; i ++)
	{
		int a, b;
		scanf("%d%d", &a, &b);
		if(A.unify(a, b))
		{
			G[a].push_back(Mp(b, ++ ptr));
			G[b].push_back(Mp(a, ptr));
		}
		else
		{
			if(B.unify(a, b))
			{
				G[a].push_back(Mp(b, ++ ptr));
				G[b].push_back(Mp(a, ptr));
			}
		}
	}
    for(int i = 1; i <= n; i ++)
	{
		if(H[i]) continue;
		H[i] = 1;
		dfs(i, 0);
	}
	return 0;
}

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

Compilation message (stderr)

pipes.cpp: In function 'int main()':
pipes.cpp:81:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   81 |  scanf("%d%d", &n, &m);
      |  ~~~~~^~~~~~~~~~~~~~~~
pipes.cpp:86:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   86 |   scanf("%d%d", &a, &b);
      |   ~~~~~^~~~~~~~~~~~~~~~

• Subtask 1: 10 / 10
• Subtask 2: 10 / 10
• Subtask 3: 10 / 10
• Subtask 4: 10 / 10
• Subtask 5: 10 / 10
• Subtask 6: 0 / 10
• Subtask 7: 0 / 10
• Subtask 8: 0 / 10
• Subtask 9: 0 / 10
• Subtask 10: 0 / 10