#include <bits/stdc++.h>
#define X first
#define Y second
using namespace std;
typedef long long llint;
const int maxn = 1e5+10;
const int base = 31337;
const int mod = 1e9+7;
const int inf = 0x3f3f3f3f;
const int logo = 18;
const int off = 1 << logo;
const int treesiz = off << 1;
int n, m;
vector< pair<int, bool> > graph[maxn];
vector< int > ops[maxn];
int parr[maxn], siz[maxn];
int dp[20][maxn];
int wh[maxn], dep[maxn];
bool bio[maxn];
int fin(int x) {
if (parr[x] == x) return x;
return parr[x] = fin(parr[x]);
}
void merg(int x, int y) {
x = fin(x);
y = fin(y);
if (x == y) return;
parr[y] = x, siz[x] += siz[y];
}
void recal(int x, int parr) {
//printf("recalculating %d %d\n", x, parr);
dp[0][x] = parr;
dep[x] = 1 + dep[parr];
bio[x] = false, wh[x] = 0;
for (int i = 1; i < 19; i++) dp[i][x] = dp[i - 1][dp[i - 1][x]];
for (auto tren : graph[x]) {
if (tren.X != parr) recal(tren.X, x);
}
}
int lif(int x, int val) {
for (int i = 0; i < 19; i++) {
if (val & (1 << i)) x = dp[i][x];
}
return x;
}
int lca(int x, int y) {
if (dep[x] > dep[y]) x = lif(x, dep[x] - dep[y]);
else y = lif(y, dep[y] - dep[x]);
if (x == y) return x;
for (int i = 18; i >= 0; i--) {
if (dp[i][x] != dp[i][y]) x = dp[i][x], y = dp[i][y];
}
return dp[0][x];
}
int dfs(int x, int par) {
int out = wh[x];
bio[x] = true;
//printf("dfs %d %d\n", x, par);
for (int i = 0; i < graph[x].size(); i++) {
auto &tren = graph[x][i];
if (tren.X == par) continue;
int kol = dfs(tren.X, x);
//printf("returned %d --> %d\n", tren, kol);
if (kol > 0) {
tren.Y = false;
int ind = ops[x][i];
graph[tren.X][ind].Y = false;
}
out = max(out, kol - 1);
}
return out;
}
int main() {
scanf("%d%d", &n, &m);
for (int i = 1; i <= n; i++) parr[i] = i, siz[i] = dep[i] = 1;
memset(bio, false, sizeof bio);
for (int i = 0; i < m; i++) {
int a, b;
scanf("%d%d", &a, &b);
if (fin(a) != fin(b)) {
//printf("edge: %d %d\n", a, b);
if (siz[fin(a)] > siz[fin(b)]) swap(a, b);
//printf("root parr: %d (%d)\n", dp[0][fin(b)], fin(b));
//assert(dp[0][fin(b)] == 0);
dfs(fin(b), 0);
recal(b, a);
merg(a, b);
ops[a].push_back(graph[b].size());
ops[b].push_back(graph[a].size());
graph[a].push_back(make_pair(b, true));
graph[b].push_back(make_pair(a, true));
} else {
int lc = lca(a, b);
wh[a] = max(wh[a], dep[a] - dep[lc]);
wh[b] = max(wh[b], dep[b] - dep[lc]);
}
}
for (int i = 1; i <= n; i++) {
int x = fin(i);
if (!bio[x]) dfs(x, 0);
}
for (int i = 1; i <= n; i++) {
for (auto tren : graph[i]) {
if (tren.Y && i < tren.X) printf("%d %d\n", i, tren.X);
}
}
return 0;
}
Compilation message
pipes.cpp: In function 'int dfs(int, int)':
pipes.cpp:71:20: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::pair<int, bool> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
71 | for (int i = 0; i < graph[x].size(); i++) {
| ~~^~~~~~~~~~~~~~~~~
pipes.cpp: In function 'int main()':
pipes.cpp:88:7: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
88 | scanf("%d%d", &n, &m);
| ~~~~~^~~~~~~~~~~~~~~~
pipes.cpp:93:8: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
93 | scanf("%d%d", &a, &b);
| ~~~~~^~~~~~~~~~~~~~~~
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
3 ms |
5196 KB |
Output is correct |
| 2 |
Correct |
3 ms |
5196 KB |
Output is correct |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
636 ms |
6076 KB |
Output is correct |
| 2 |
Correct |
246 ms |
5964 KB |
Output is correct |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
601 ms |
5680 KB |
Output is correct |
| 2 |
Correct |
264 ms |
5708 KB |
Output is correct |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
3702 ms |
6768 KB |
Output is correct |
| 2 |
Correct |
930 ms |
6668 KB |
Output is correct |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Execution timed out |
5050 ms |
8776 KB |
Time limit exceeded |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Execution timed out |
5095 ms |
14568 KB |
Time limit exceeded |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Execution timed out |
5062 ms |
15872 KB |
Time limit exceeded |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Execution timed out |
5092 ms |
18400 KB |
Time limit exceeded |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Execution timed out |
5084 ms |
18304 KB |
Time limit exceeded |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Execution timed out |
5085 ms |
17660 KB |
Time limit exceeded |
| 2 |
Halted |
0 ms |
0 KB |
- |
