#undef _GLIBCXX_DEBUG // disable run-time bound checking, etc
#pragma GCC optimize("Ofast,inline") // Ofast = O3,fast-math,allow-store-data-races,no-protect-parens
#pragma GCC optimize ("unroll-loops")
#pragma GCC target("bmi,bmi2,lzcnt,popcnt") // bit manipulation
#pragma GCC target("movbe") // byte swap
#pragma GCC target("aes,pclmul,rdrnd") // encryption
#pragma GCC target("avx,avx2,f16c,fma,sse3,ssse3,sse4.1,sse4.2") // SIMD
#include <bits/stdc++.h>
#include <bits/extc++.h>
using namespace std;
#define enablell 1
typedef long long ll;
typedef unsigned long long ull;
#if enablell
#define int ll
#define inf int(1e18)
#define float double
#else
const int inf = int(2e9);
#endif
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef vector<vvi> vvvi;
typedef vector<vvvi> vvvvi;
typedef vector<bool> vb;
typedef vector<vb> vvb;
typedef vector<vvb> vvvb;
typedef pair<int, int> p2;
typedef vector<p2> vp2;
typedef vector<vp2> vvp2;
typedef vector<vvp2> vvvp2;
typedef tuple<int, int, int> p3;
typedef vector<p3> vp3;
typedef vector<vp3> vvp3;
typedef vector<vvp3> vvvp3;
typedef tuple<int, int, int, int> p4;
typedef vector<p4> vp4;
#define PBDS 0
#define _LOCAL _MSC_VER > 0
#if _LOCAL
#define gc() getchar()
#define popcount(x) __popcnt(x)
#define leading_zeros(x) _lzcnt_u32(x)
uint32_t clz(uint32_t x) { return _lzcnt_u32(x); }
uint32_t ctz(uint32_t x) { return _tzcnt_u32(x); }
#define bswap64(x) _byteswap_uint64(x)
#define assert(x) debassert(x)
#else
#define popcount(x) __builtin_popcount(x)
uint32_t clz(uint32_t x) { return __builtin_clz(x); }
uint32_t ctz(uint32_t x) { return __builtin_ctzll(x); }
#define bswap64(x) __builtin_bswap64(x)
#define gc() getchar_unlocked()
#if PBDS
using namespace __gnu_pbds;
// lower_bound is now upper_bound and vice versa (multiset). generally a bit broken
template<typename T> using indexed_multiset = tree<int, null_type, less_equal<T>, rb_tree_tag, tree_order_statistics_node_update>;
template<typename T> using indexed_set = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
struct chash { // large odd number for C
const uint64_t C = ll(4e18 * acos(0)) | 71;
ll operator()(ll x) const { return __builtin_bswap64(x * C); }
};
template<typename T, typename U> using fast_map = __gnu_pbds::gp_hash_table<T, U, chash>;
template<typename T> using fast_set = __gnu_pbds::gp_hash_table<T, null_type, chash>;
template<typename T, typename H> using fast_set_h = __gnu_pbds::gp_hash_table<T, null_type, H>;
#endif
#endif
#define FAST_INPUT 0
#define FILE_TC 0
#if FILE_TC && _LOCAL
ifstream filein("E:\\desktop\\code\\repos\\Comp prog\\x64\\Debug\\in.txt");
//ifstream filein("E:\\downloads\\test_data\\test_data\\005-case05.in");
//ifstream filein("E:\\desktop\\po-repos\\swedish-olympiad-2023\\online\\tomtplanering\\data\\secret\\group10\\010-case10.in");
#define cin filein
//ifstream cin("C:\\Users\\Matis\\desktop\\po-two\\swedish-olympiad-2014\\");
void fast() {}
#else
inline void fast() { ios::sync_with_stdio(false); cin.tie(NULL); cout.tie(NULL); }
#endif
#if FAST_INPUT && !FILE_TC
inline void read(int& v) { v = 0; int sign = 1; char c = gc(); if (c == '-') { sign = -1; } else { v += c - '0'; } while ((c = gc()) != EOF && c != ' ' && c != '\n') { v *= 10; v += c - '0'; } v *= sign; }
inline void read(int& u, int& v) { read(u); read(v); }
inline void read(int& u, int& v, int& k) { read(u); read(v); read(k); }
//inline void read(int& v) { char c; while ((c = getchar()) != EOF && c != ' ' && c != '\n') { v *= 10; v += c - '0'; } }
inline void read(string& s) { char c; while ((c = gc()) != EOF && c != '\n' && c != ' ') { s.push_back(c); } }
#else
template <typename T> inline void read(T& a) { cin >> a; }
template <typename T> inline void read(T& a, T& b) { cin >> a >> b; }
template <typename T> inline void read(T& a, T& b, T& c) { cin >> a >> b >> c; }
#endif
template <typename T> inline void write(T a) { cout << (a) << "\n"; }
#define quit cout << endl; _Exit(0);
#define dread(type, a) type a; read(a)
#define dread2(type, a, b) dread(type, a); dread(type, b)
#define dread3(type, a, b, c) dread2(type, a, b); dread(type, c)
#define dread4(type, a, b, c, d) dread3(type, a, b, c); dread(type, d)
#define dread5(type, a, b, c, d, e) dread4(type, a, b, c, d); dread(type, e)
#define readvector(type, name, size) vector<type> name(size); rep(i,size) {dread(type,temp); name[i]=temp;}
#ifdef _DEBUG
#define noop cout << "";
#define deb __debugbreak();
#define debassert(expr) if (!(expr)) deb;
#define debif(expr) if(expr) deb;
#else
#define noop ;
#define deb ;
#define debassert(expr) ;
#define debif(expr) ;
#endif
#define rep(i, high) for (int i = 0; i < high; i++)
#define repp(i, low, high) for (int i = low; i < high; i++)
#define repe(i, container) for (auto& i : container)
#define per(i, high) for (int i = high-1; i >= 0; i--)
#define perr(i, low, high) for (int i = high-1; i >= low; i--)
#define all(a) a.begin(),a.end()
#define rall(a) a.rbegin(),a.rend()
#define setcontains(set, x) (set.find(x) != set.end())
#define within(a, b, c, d) (a >= 0 && a < b && c >= 0 && c < d)
#define sz(container) ((int)container.size())
#define mp(a,b) (make_pair(a,b))
#define ceildiv(x,y) ((x + y - 1) / y)
template<typename T> inline void eraseOne(multiset<T>& mSet, T k) { auto itr = mSet.find(k); if (itr != mSet.end()) { mSet.erase(itr); } }
template<typename T, typename U> inline T first(U& a) { return *begin(a); }
template <typename T, typename U> inline void operator+=(pair<T, U>& l, const pair<T, U>& r) { l = { l.first + r.first,l.second + r.second }; }
template <typename T, typename U> inline pair<T, U> operator+(const pair<T, U> l, const pair<T, U> r) { return { l.first + r.first, l.second + r.second }; }
template <typename T, typename U> inline pair<T, U> operator-(const pair<T, U> l, const pair<T, U> r) { return { l.first - r.first, l.second - r.second }; }
template <typename T, typename U> inline pair<T, U> operator*(const pair<T, U> l, const int m) { return { l.first * m, l.second * m }; }
template <typename Out> inline void split(const string& s, char delim, Out result) { istringstream iss(s); string item; while (getline(iss, item, delim)) { *result++ = item; } }
inline vector<string> split(const string& s, char delim) { vector<string> elems; split(s, delim, back_inserter(elems)); return elems; }
vector<string> split(string s, string d) { size_t k = 0, n, e = d.length(); string t; vector<string> r; while ((n = s.find(d, k)) != string::npos) { t = s.substr(k, n - k); k = n + e; r.push_back(t); } r.push_back(s.substr(k)); return r; }
ll binpow(ll a, ll b) { ll res = 1; while (b > 0) { if (b & 1) res = res * a; a = a * a; b >>= 1; } return res; }
ll binpow(ll a, ll b, ll m) { a %= m; long long res = 1; while (b > 0) { if (b & 1) res = res * a % m; a = a * a % m; b >>= 1; } return res; } // For a < 2^31
#if 1
auto Start = chrono::high_resolution_clock::now();
void resettimer() { Start = chrono::high_resolution_clock::now(); }
int elapsedmillis() { return chrono::duration_cast<chrono::milliseconds>(chrono::high_resolution_clock::now() - Start).count(); }
random_device rd;
mt19937 rng(rd());
template<typename T> inline T randint(T lo, T hi) { return uniform_int_distribution<T>(lo, hi)(rng); } // [lo,hi]
template<typename T> inline T randel(vector<T>& v) { return v[uniform_int_distribution<T>((int)0, v.size() - 1)(rng)]; } // [lo,hi]
#endif
const ll mod = 1e9 + 7;
vp2 dirs = { {0,1},{0,-1},{1,0},{-1,0} };
void dfs(int u, int p, vvi& edges, vi& leafs)
{
if (edges[u].size()==1)
{
leafs.push_back(u);
}
repe(e, edges[u])
{
if (e != p) dfs(e, u, edges, leafs);
}
}
vi par;
vi numleafs;
vvi children;
int dfs2(int u, int p, vvi& edges)
{
par[u] = p;
int ret = 0;
if (edges[u].size()==1)
{
ret++;
}
repe(e, edges[u])
{
if (e == p) continue;
int k = dfs2(e, u, edges);
children[u].push_back(k);
ret += k;
}
return numleafs[u]=ret;
}
int32_t main()
{
fast();
dread(int, n);
vvi edges(n);
if (n==2)
{
cout << "1\n";
cout << "1 2";
quit;
}
rep(i, n - 1)
{
dread2(int, a, b);
a--; b--;
edges[a].push_back(b);
edges[b].push_back(a);
}
numleafs.resize(n);
par.resize(n);
children.resize(n);
dfs2(0, -1, edges);
int newroot;
int bestscore = inf;
rep(i, n)
{
int largestsub = 0;
if (i!=0)
{
largestsub = max(largestsub, numleafs[par[i]] - numleafs[i]);
}
repe(c, children[i]) largestsub = max(largestsub, c);
if (largestsub<bestscore && edges[i].size() != 1)
{
newroot = i;
bestscore = largestsub;
}
}
vvi leafs;
priority_queue<p2> pq;
repe(e, edges[newroot])
{
vi leaf;
dfs(e, newroot, edges, leaf);
pq.emplace(leaf.size(), leafs.size());
leafs.push_back(leaf);
}
vp2 ans;
while (pq.size()>1)
{
p2 a = pq.top();
pq.pop();
p2 b = pq.top();
pq.pop();
ans.emplace_back(leafs[a.second].back(), leafs[b.second].back());
leafs[a.second].pop_back();
leafs[b.second].pop_back();
if (leafs[a.second].size())
{
pq.emplace(leafs[a.second].size(), a.second);
}
if (leafs[b.second].size())
{
pq.emplace(leafs[b.second].size(), b.second);
}
}
if (pq.size())
{
int a, b;
tie(a, b) = pq.top();
pq.pop();
ans.emplace_back(leafs[b].back(), newroot);
//assert(leafs[b].size() == 1);
}
cout << ans.size() << "\n";
repe(e, ans)
{
cout << e.first + 1 << " " << e.second + 1 << "\n";
}
quit;
}
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
1 ms |
212 KB |
Output is correct |
| 2 |
Correct |
0 ms |
212 KB |
Output is correct |
| 3 |
Correct |
1 ms |
212 KB |
Output is correct |
| 4 |
Correct |
0 ms |
212 KB |
Output is correct |
| 5 |
Correct |
0 ms |
212 KB |
Output is correct |
| 6 |
Correct |
1 ms |
212 KB |
Output is correct |
| 7 |
Correct |
0 ms |
212 KB |
Output is correct |
| 8 |
Incorrect |
1 ms |
212 KB |
Breaking single line is causing network to disconnect. |
| 9 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
1 ms |
212 KB |
Output is correct |
| 2 |
Correct |
0 ms |
212 KB |
Output is correct |
| 3 |
Correct |
1 ms |
212 KB |
Output is correct |
| 4 |
Correct |
0 ms |
212 KB |
Output is correct |
| 5 |
Correct |
0 ms |
212 KB |
Output is correct |
| 6 |
Correct |
1 ms |
212 KB |
Output is correct |
| 7 |
Correct |
0 ms |
212 KB |
Output is correct |
| 8 |
Incorrect |
1 ms |
212 KB |
Breaking single line is causing network to disconnect. |
| 9 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
1 ms |
212 KB |
Output is correct |
| 2 |
Correct |
0 ms |
212 KB |
Output is correct |
| 3 |
Correct |
1 ms |
212 KB |
Output is correct |
| 4 |
Correct |
0 ms |
212 KB |
Output is correct |
| 5 |
Correct |
0 ms |
212 KB |
Output is correct |
| 6 |
Correct |
1 ms |
212 KB |
Output is correct |
| 7 |
Correct |
0 ms |
212 KB |
Output is correct |
| 8 |
Incorrect |
1 ms |
212 KB |
Breaking single line is causing network to disconnect. |
| 9 |
Halted |
0 ms |
0 KB |
- |
