#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef long double ld;
typedef double db;
typedef string str;
typedef pair<int,int> pi;
typedef pair<ll,ll> pl;
typedef pair<db,db> pd;
typedef vector<int> vi;
typedef vector<ll> vl;
typedef vector<db> vd;
typedef vector<str> vs;
typedef vector<pi> vpi;
typedef vector<pl> vpl;
typedef vector<pd> vpd;
#define mp make_pair
#define f first
#define s second
#define sz(x) (int)x.size()
#define all(x) begin(x), end(x)
#define rall(x) (x).rbegin(), (x).rend()
#define rsz resize
#define ins insert
#define ft front()
#define bk back()
#define pf push_front
#define pb push_back
#define eb emplace_back
#define lb lower_bound
#define ub upper_bound
#define FOR(i,a,b) for (int i = (a); i < (b); ++i)
#define F0R(i,a) FOR(i,0,a)
#define ROF(i,a,b) for (int i = (b)-1; i >= (a); --i)
#define R0F(i,a) ROF(i,0,a)
#define trav(a,x) for (auto& a: x)
const int MOD = 1e9+7; // 998244353;
const int MX = 2e5+5;
const ll INF = 1e18;
const ld PI = acos((ld)-1);
const int xd[4] = {1,0,-1,0}, yd[4] = {0,1,0,-1};
mt19937 rng((uint32_t)chrono::steady_clock::now().time_since_epoch().count());
template<class T> bool ckmin(T& a, const T& b) {
return b < a ? a = b, 1 : 0; }
template<class T> bool ckmax(T& a, const T& b) {
return a < b ? a = b, 1 : 0; }
int pct(int x) { return __builtin_popcount(x); }
int bits(int x) { return 31-__builtin_clz(x); } // floor(log2(x))
int cdiv(int a, int b) { return a/b+!(a<0||a%b == 0); } // division of a by b rounded up, assumes b > 0
int fstTrue(function<bool(int)> f, int lo, int hi) {
hi ++; assert(lo <= hi); // assuming f is increasing
while (lo < hi) { // find first index such that f is true
int mid = (lo+hi)/2;
f(mid) ? hi = mid : lo = mid+1;
}
return lo;
}
// INPUT
template<class A> void re(complex<A>& c);
template<class A, class B> void re(pair<A,B>& p);
template<class A> void re(vector<A>& v);
template<class A, size_t SZ> void re(array<A,SZ>& a);
template<class T> void re(T& x) { cin >> x; }
void re(db& d) { str t; re(t); d = stod(t); }
void re(ld& d) { str t; re(t); d = stold(t); }
template<class H, class... T> void re(H& h, T&... t) { re(h); re(t...); }
template<class A> void re(complex<A>& c) { A a,b; re(a,b); c = {a,b}; }
template<class A, class B> void re(pair<A,B>& p) { re(p.f,p.s); }
template<class A> void re(vector<A>& x) { trav(a,x) re(a); }
template<class A, size_t SZ> void re(array<A,SZ>& x) { trav(a,x) re(a); }
// TO_STRING
#define ts to_string
str ts(char c) { return str(1,c); }
str ts(bool b) { return b ? "true" : "false"; }
str ts(const char* s) { return (str)s; }
str ts(str s) { return s; }
template<class A> str ts(complex<A> c) {
stringstream ss; ss << c; return ss.str(); }
str ts(vector<bool> v) {
str res = "{"; F0R(i,sz(v)) res += char('0'+v[i]);
res += "}"; return res; }
template<size_t SZ> str ts(bitset<SZ> b) {
str res = ""; F0R(i,SZ) res += char('0'+b[i]);
return res; }
template<class A, class B> str ts(pair<A,B> p);
template<class T> str ts(T v) { // containers with begin(), end()
bool fst = 1; str res = "{";
for (const auto& x: v) {
if (!fst) res += ", ";
fst = 0; res += ts(x);
}
res += "}"; return res;
}
template<class A, class B> str ts(pair<A,B> p) {
return "("+ts(p.f)+", "+ts(p.s)+")"; }
// OUTPUT
template<class A> void pr(A x) { cout << ts(x); }
template<class H, class... T> void pr(const H& h, const T&... t) {
pr(h); pr(t...); }
void ps() { pr("\n"); } // print w/ spaces
template<class H, class... T> void ps(const H& h, const T&... t) {
pr(h); if (sizeof...(t)) pr(" "); ps(t...); }
// DEBUG
void DBG() { cerr << "]" << endl; }
template<class H, class... T> void DBG(H h, T... t) {
cerr << ts(h); if (sizeof...(t)) cerr << ", ";
DBG(t...); }
#ifdef LOCAL // compile with -DLOCAL
#define dbg(...) cerr << "LINE(" << __LINE__ << ") -> [" << #__VA_ARGS__ << "]: [", DBG(__VA_ARGS__)
#else
#define dbg(...) 0
#endif
// FILE I/O
void setIn(string s) { freopen(s.c_str(),"r",stdin); }
void setOut(string s) { freopen(s.c_str(),"w",stdout); }
void unsyncIO() { ios_base::sync_with_stdio(0); cin.tie(0); }
void setIO(string s = "") {
unsyncIO();
// cin.exceptions(cin.failbit);
// throws exception when do smth illegal
// ex. try to read letter into int
if (sz(s)) { setIn(s+".in"), setOut(s+".out"); } // for USACO
}
/**
* Description: Disjoint Set Union with path compression
* and union by size. Add edges and test connectivity.
* Use for Kruskal's or Boruvka's minimum spanning tree.
* Time: O(\alpha(N))
* Source: CSAcademy, KACTL
* Verification: USACO superbull
*/
struct DSU {
vi e; void init(int n) { e = vi(n,-1); }
int get(int x) { return e[x] < 0 ? x : e[x] = get(e[x]); }
bool sameSet(int a, int b) { return get(a) == get(b); }
int size(int x) { return -e[get(x)]; }
bool unite(int x, int y) { // union by size
x = get(x), y = get(y); if (x == y) return 0;
if (e[x] > e[y]) swap(x,y);
e[x] += e[y]; e[y] = x; return 1;
}
};
vector<vi> adj; //may not be connected
vi q; //query number for each node
vi qnum; //# left for each query number
vector<vi> qlist; //nodes for each query number
vi num; //-sz at each lca
vpi ans;
struct LCAOff {
vi e; //-index of highest node in component
vi depth;
int get(int x) { return e[x] < 0 ? x : e[x] = get(e[x]); }
bool sameSet(int a, int b) { return get(a) == get(b); }
int tope(int x) { return -e[get(x)]; }
bool unite(int x, int y) { // union by size, node, parent
x = get(x), y = get(y);
if (x == y) return 0;
int hi = e[y];
if (e[x] > e[y]) swap(x,y);
e[x] += e[y]; e[y] = x;
e[x] = hi;
return 1;
}
void dfs(int node, int prv = -1){
if(prv == -1){
depth[node] = 0;
}
else{
depth[node] = depth[prv]+1;
}
qnum[q[node]]--;
if(qnum[q[node]] == 0){ //process query
int hi = node;
int curd = depth[node];
for(auto u: qlist[q[node]]){
if(depth[tope(u)] < curd){
hi = tope(u);
curd = depth[hi];
}
}
num[hi]-=sz(qlist[q[node]]);
}
for(auto u: adj[node]){
if(u == prv) continue;
dfs(u, node);
}
if(prv != -1) unite(node, prv);
}
void prop(int node, int prv = -1){
for(auto u: adj[node]){
if(u == prv) continue;
prop(u, node);
num[node]+=num[u];
}
if(prv != -1 && num[node] == 0){
ans.pb(mp(node, prv));
}
}
void init(int n) {
e = vi(n+1,-1);
depth = vi(n+1, -1);
for(int i = 1; i <= n; i++){
e[i] = -i;
num[i]++;
}
for(int i = 1; i <= n; i++){
if(depth[i] != -1) continue;
dfs(i);
prop(i);
}
}
};
DSU span; //use to get tree span edges
DSU ext; //use to get q
LCAOff gen;
int main() {
setIO();
int N, M;
cin >> N >> M;
span.init(N+1);
ext.init(N+1);
for(int i = 0; i <= N; i++){
adj.pb(vi{});
}
for(int i = 1; i <= M; i++){
int u, v;
cin >> u >> v;
if(span.unite(u, v)){
adj[u].pb(v);
adj[v].pb(u);
}
else{
ext.unite(u, v);
}
}
span.e.clear();
q = vi(N+1, 0);
qnum = vi(N+1, 0);
for(int i = 0; i <= N; i++){
qlist.pb(vi{});
}
num = vi(N+1, 0);
for(int i = 1; i <= N; i++){
q[i] = ext.get(i);
qnum[q[i]]++;
qlist[q[i]].pb(i);
}
ext.e.clear();
gen.init(N);
for(auto u: ans){
ps(u.f, u.s);
}
// you should actually read the stuff at the bottom
}
/* stuff you should look for
* int overflow, array bounds
* special cases (n=1?)
* do smth instead of nothing and stay organized
* WRITE STUFF DOWN
*/
Compilation message
pipes.cpp: In function 'void setIn(std::__cxx11::string)':
pipes.cpp:128:31: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result]
void setIn(string s) { freopen(s.c_str(),"r",stdin); }
~~~~~~~^~~~~~~~~~~~~~~~~~~~~
pipes.cpp: In function 'void setOut(std::__cxx11::string)':
pipes.cpp:129:32: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result]
void setOut(string s) { freopen(s.c_str(),"w",stdout); }
~~~~~~~^~~~~~~~~~~~~~~~~~~~~~
| # |
결과 |
실행 시간 |
메모리 |
Grader output |
| 1 |
Correct |
1 ms |
384 KB |
Output is correct |
| 2 |
Correct |
0 ms |
384 KB |
Output is correct |
| # |
결과 |
실행 시간 |
메모리 |
Grader output |
| 1 |
Correct |
5 ms |
960 KB |
Output is correct |
| 2 |
Correct |
4 ms |
960 KB |
Output is correct |
| # |
결과 |
실행 시간 |
메모리 |
Grader output |
| 1 |
Correct |
103 ms |
760 KB |
Output is correct |
| 2 |
Correct |
102 ms |
760 KB |
Output is correct |
| # |
결과 |
실행 시간 |
메모리 |
Grader output |
| 1 |
Correct |
168 ms |
1548 KB |
Output is correct |
| 2 |
Correct |
200 ms |
1524 KB |
Output is correct |
| # |
결과 |
실행 시간 |
메모리 |
Grader output |
| 1 |
Correct |
333 ms |
3184 KB |
Output is correct |
| 2 |
Correct |
260 ms |
4080 KB |
Output is correct |
| # |
결과 |
실행 시간 |
메모리 |
Grader output |
| 1 |
Correct |
430 ms |
9956 KB |
Output is correct |
| 2 |
Correct |
400 ms |
9908 KB |
Output is correct |
| # |
결과 |
실행 시간 |
메모리 |
Grader output |
| 1 |
Correct |
659 ms |
10788 KB |
Output is correct |
| 2 |
Correct |
658 ms |
10724 KB |
Output is correct |
| # |
결과 |
실행 시간 |
메모리 |
Grader output |
| 1 |
Correct |
887 ms |
12172 KB |
Output is correct |
| 2 |
Correct |
842 ms |
12136 KB |
Output is correct |
| # |
결과 |
실행 시간 |
메모리 |
Grader output |
| 1 |
Correct |
1095 ms |
12004 KB |
Output is correct |
| 2 |
Correct |
1082 ms |
12136 KB |
Output is correct |
| # |
결과 |
실행 시간 |
메모리 |
Grader output |
| 1 |
Correct |
1449 ms |
11560 KB |
Output is correct |
| 2 |
Correct |
1260 ms |
12804 KB |
Output is correct |
