Submission #378453

#	Time	Username	Problem	Language	Result	Execution time	Memory
378453		AriaH	Pipes (CEOI15_pipes)	C++11	100 / 100	1581 ms	14316 KiB

pipes

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

#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()

const int N = 1e5 + 5;
const ll mod = 1e9 + 7;
const ll mod2 = 998244353;
const ll inf = 8e18;
const int LOG = 22;

int par[N * 2];

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;
}

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

vector < int > G[N];

void dfs(int v, int P = -1)
{
	Up[v] = H[v];
	int id = -1;
	for(auto u : G[v])
	{
		id ++;
		if(u == P) continue;
		if(H[u])
		{
			Up[v] = min(Up[v], H[u]);
		}
		else
		{
			H[u] = H[v] + 1;
			dfs(u, v);
			if(Up[u] > H[v] && (id > 0 && G[v][id - 1] == u) == 0 && (id + 1 < SZ(G[v]) && G[v][id + 1] == u) == 0)
			{
				printf("%d %d\n", v, u);
			}
			Up[v] = min(Up[v], Up[u]);
		}
	}
}

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

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

Compilation message (stderr)

pipes.cpp: In function 'int main()':
pipes.cpp:69:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   69 |  scanf("%d%d", &n, &m);
      |  ~~~~~^~~~~~~~~~~~~~~~
pipes.cpp:73:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   73 |   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: 10 / 10
• Subtask 7: 10 / 10
• Subtask 8: 10 / 10
• Subtask 9: 10 / 10
• Subtask 10: 10 / 10