#include <bits/stdc++.h>
using namespace std;
//#define FILE_IO
typedef pair<int, int> pii;
int N, M;
int K, vis[100005], lst[100005];
vector<int> nodes, edg[100005];
vector<pii> critical;
int q[100005];
int f[2][100005];
void init(int id, int N)
{
for(int i = 1; i <= N; i++) f[id][i] = i;
}
int F(int id, int x)
{
if(f[id][x] == x) return x;
return f[id][x] = F(id, f[id][x]);
}
void unite(int id, int x, int y)
{
if(F(id, x) == F(id, y)) return;
f[id][F(id, y)] = F(id, x);
}
/*class UnionFind
{
public:
int N;
int f[100005];
void init(int _N)
{
N = _N;
for(int i = 1; i <= N; i++) f[i] = i;
}
int F(int x)
{
if(f[x] == x) return x;
return f[x] = F(f[x]);
}
void unite(int x, int y)
{
if(F(x) == F(y)) return;
f[F(y)] = F(x);
}
};
UnionFind f[2];*/
void gen()
{
freopen("1.in", "w", stdout);
int N = 10000;
int M = 1e6;
printf("%d %d\n", N, M);
auto seed = chrono::high_resolution_clock::now().time_since_epoch().count();
mt19937 gene(seed);
uniform_int_distribution<int> uid(1, N);
for(int i = 1; i <= M; i++)
{
int x = uid(gene);
int y = uid(gene);
printf("%d %d\n", x, y);
}
exit(0);
}
int main()
{
//gen();
#ifdef FILE_IO
freopen("1.in", "r", stdin);
freopen("1.out", "w", stdout);
#endif
scanf("%d%d", &N, &M);
init(0, N), init(1, N);
int mx = 0;
for(int i = 1; i <= M; i++)
{
/*int cnt = 0;
for(int i = 1; i <= N; i++)
cnt += edg[i].size();
mx = max(mx, cnt);
assert(critical.size() <= N);*/
int x, y;
scanf("%d%d", &x, &y);
if(F(0, x) != F(0, y))
{
critical.push_back({x, y});
unite(0, x, y);
int fx = F(1, x);
int fy = F(1, y);
edg[fx].push_back(fy);
edg[fy].push_back(fx);
continue;
}
if(F(1, x) == F(1, y)) continue;
x = F(1, x);
y = F(1, y);
nodes.clear();
nodes.push_back(x);
nodes.push_back(y);
K += 2;
vis[x] = K; vis[y] = K + 1;
int st = 1, dr = 2;
q[1] = x;
q[2] = y;
while(st <= dr)
{
int nod = q[st];
int id = vis[nod];
st++;
for(auto nxt: edg[nod])
{
nxt = F(1, nxt);
if(vis[nxt] == id) continue;
if(vis[nxt] == (id ^ 1))
{
int nd1 = nod;
int nd2 = nxt;
if(vis[nod] != K) swap(nd1, nd2);
while(nd1 != x)
{
nodes.push_back(nd1);
nd1 = lst[nd1];
}
while(nd2 != y)
{
nodes.push_back(nd2);
nd2 = lst[nd2];
}
st = dr + 1;
break;
}
vis[nxt] = vis[nod];
lst[nxt] = nod;
q[++dr] = nxt;
}
}
for(int i = 1; i < nodes.size(); i++)
{
unite(1, nodes[0], nodes[i]);
for(auto x: edg[ nodes[i] ])
if(F(1, x) != F(1, nodes[0]))
edg[ nodes[0] ].push_back(x);
edg[ nodes[i] ].clear();
}
for(int i = 0; i < edg[ nodes[0] ].size(); i++)
{
if(F( 1, nodes[0] ) == F( 1, edg[ nodes[0] ][i]))
{
edg[ nodes[0] ].erase(edg[ nodes[0] ].begin() + i);
i--;
}
}
for(int i = 0; i < critical.size(); i++)
if( F(1, critical[i].first) == F(1, critical[i].second) )
{
critical.erase(critical.begin() + i);
i--;
}
}
for(auto e: critical)
if(F(1, e.first) != F(1, e.second))
printf("%d %d\n", e.first, e.second);
//cerr << mx << '\n';
return 0;
}
Compilation message
pipes.cpp: In function 'int main()':
pipes.cpp:165:26: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
for(int i = 1; i < nodes.size(); i++)
~~^~~~~~~~~~~~~~
pipes.cpp:173:26: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
for(int i = 0; i < edg[ nodes[0] ].size(); i++)
~~^~~~~~~~~~~~~~~~~~~~~~~~
pipes.cpp:182:26: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
for(int i = 0; i < critical.size(); i++)
~~^~~~~~~~~~~~~~~~~
pipes.cpp:89:9: warning: unused variable 'mx' [-Wunused-variable]
int mx = 0;
^~
pipes.cpp: In function 'void gen()':
pipes.cpp:60:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result]
freopen("1.in", "w", stdout);
~~~~~~~^~~~~~~~~~~~~~~~~~~~~
pipes.cpp: In function 'int main()':
pipes.cpp:86:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
scanf("%d%d", &N, &M);
~~~~~^~~~~~~~~~~~~~~~
pipes.cpp:101:14: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
scanf("%d%d", &x, &y);
~~~~~^~~~~~~~~~~~~~~~
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
4 ms |
2688 KB |
Output is correct |
| 2 |
Correct |
3 ms |
2688 KB |
Output is correct |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
45 ms |
7032 KB |
Output is correct |
| 2 |
Correct |
30 ms |
3576 KB |
Output is correct |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
139 ms |
5844 KB |
Output is correct |
| 2 |
Correct |
128 ms |
3272 KB |
Output is correct |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Runtime error |
399 ms |
21828 KB |
Memory limit exceeded (if you are sure your verdict is not MLE, please contact us) |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Runtime error |
912 ms |
65536 KB |
Execution killed with signal 9 (could be triggered by violating memory limits) |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Runtime error |
1711 ms |
65536 KB |
Execution killed with signal 9 (could be triggered by violating memory limits) |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Runtime error |
1967 ms |
65536 KB |
Execution killed with signal 9 (could be triggered by violating memory limits) |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Runtime error |
2362 ms |
65536 KB |
Execution killed with signal 9 (could be triggered by violating memory limits) |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Runtime error |
2395 ms |
65536 KB |
Execution killed with signal 9 (could be triggered by violating memory limits) |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Runtime error |
2388 ms |
65536 KB |
Execution killed with signal 9 (could be triggered by violating memory limits) |
| 2 |
Halted |
0 ms |
0 KB |
- |
