Submission #313436

#TimeUsernameProblemLanguageResultExecution timeMemory
313436BenqTorrent (COI16_torrent)C++14
100 / 100
152 ms26140 KiB
#include <bits/stdc++.h> using namespace std; using ll = long long; using ld = long double; using db = double; using str = string; // yay python! using pi = pair<int,int>; using pl = pair<ll,ll>; using pd = pair<db,db>; using vi = vector<int>; using vb = vector<bool>; using vl = vector<ll>; using vd = vector<db>; using vs = vector<str>; using vpi = vector<pi>; using vpl = vector<pl>; using vpd = vector<pd>; #define tcT template<class T // ^ lol this makes everything look weird but I'll try it tcT> using V = vector<T>; tcT, size_t SZ> using AR = array<T,SZ>; // pairs #define mp make_pair #define f first #define s second // vectors #define sz(x) (int)(x).size() #define all(x) begin(x), end(x) #define rall(x) (x).rbegin(), (x).rend() #define sor(x) sort(all(x)) #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 // loops #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 = 3e5+5; const ll INF = 1e18; // not too close to LLONG_MAX const ld PI = acos((ld)-1); const int xd[4] = {1,0,-1,0}, yd[4] = {0,1,0,-1}; // for every grid problem!! mt19937 rng((uint32_t)chrono::steady_clock::now().time_since_epoch().count()); // helper funcs constexpr int pct(int x) { return __builtin_popcount(x); } // # of bits set constexpr int bits(int x) { return 31-__builtin_clz(x); } // floor(log2(x)) ll cdiv(ll a, ll b) { return a/b+((a^b)>0&&a%b); } // divide a by b rounded up ll fdiv(ll a, ll b) { return a/b-((a^b)<0&&a%b); } // divide a by b rounded down tcT> bool ckmin(T& a, const T& b) { return b < a ? a = b, 1 : 0; } // set a = min(a,b) tcT> bool ckmax(T& a, const T& b) { return a < b ? a = b, 1 : 0; } #define tcTU tcT, class U tcTU> T fstTrue(T lo, T hi, U f) { hi ++; assert(lo <= hi); // assuming f is increasing while (lo < hi) { // find first index such that f is true T mid = lo+(hi-lo)/2; f(mid) ? hi = mid : lo = mid+1; } return lo; } tcTU> T lstTrue(T lo, T hi, U f) { lo --; assert(lo <= hi); // assuming f is decreasing while (lo < hi) { // find first index such that f is true T mid = lo+(hi-lo+1)/2; f(mid) ? lo = mid : hi = mid-1; } return lo; } tcT> void remDup(vector<T>& v) { // sort and remove duplicates sort(all(v)); v.erase(unique(all(v)),end(v)); } tcTU> void erase(T& t, const U& u) { // don't erase auto it = t.find(u); assert(it != end(t)); t.erase(u); } // element that doesn't exist from (multi)set // INPUT #define tcTUU tcT, class ...U tcT> void re(complex<T>& c); tcTU> void re(pair<T,U>& p); tcT> void re(vector<T>& v); tcT, size_t SZ> void re(AR<T,SZ>& a); tcT> 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); } tcTUU> void re(T& t, U&... u) { re(t); re(u...); } tcT> void re(complex<T>& c) { T a,b; re(a,b); c = {a,b}; } tcTU> void re(pair<T,U>& p) { re(p.f,p.s); } tcT> void re(vector<T>& x) { trav(a,x) re(a); } tcT, size_t SZ> void re(AR<T,SZ>& x) { trav(a,x) re(a); } // TO_STRING #define ts to_string str ts(char c) { return str(1,c); } str ts(const char* s) { return (str)s; } str ts(str s) { return s; } str ts(bool b) { #ifdef LOCAL return b ? "true" : "false"; #else return ts((int)b); #endif } tcT> str ts(complex<T> 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; } tcTU> str ts(pair<T,U> p); tcT> str ts(T v) { // containers with begin(), end() #ifdef LOCAL bool fst = 1; str res = "{"; for (const auto& x: v) { if (!fst) res += ", "; fst = 0; res += ts(x); } res += "}"; return res; #else bool fst = 1; str res = ""; for (const auto& x: v) { if (!fst) res += " "; fst = 0; res += ts(x); } return res; #endif } tcTU> str ts(pair<T,U> p) { #ifdef LOCAL return "("+ts(p.f)+", "+ts(p.s)+")"; #else return ts(p.f)+" "+ts(p.s); #endif } // OUTPUT tcT> void pr(T x) { cout << ts(x); } tcTUU> void pr(const T& t, const U&... u) { pr(t); pr(u...); } void ps() { pr("\n"); } // print w/ spaces tcTUU> void ps(const T& t, const U&... u) { pr(t); if (sizeof...(u)) pr(" "); ps(u...); } // DEBUG void DBG() { cerr << "]" << endl; } tcTUU> void DBG(const T& t, const U&... u) { cerr << ts(t); if (sizeof...(u)) cerr << ", "; DBG(u...); } #ifdef LOCAL // compile with -DLOCAL, chk -> fake assert #define dbg(...) cerr << "Line(" << __LINE__ << ") -> [" << #__VA_ARGS__ << "]: [", DBG(__VA_ARGS__) #define chk(...) if (!(__VA_ARGS__)) cerr << "Line(" << __LINE__ << ") -> function(" \ << __FUNCTION__ << ") -> CHK FAILED: (" << #__VA_ARGS__ << ")" << "\n", exit(0); #else #define dbg(...) 0 #define chk(...) 0 #endif // FILE I/O void setIn(str s) { freopen(s.c_str(),"r",stdin); } void setOut(str s) { freopen(s.c_str(),"w",stdout); } void unsyncIO() { cin.tie(0)->sync_with_stdio(0); } void setIO(str 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 } int N,A,B,par[MX]; bool inPath[MX]; vi adj[MX]; void dfs(int x) { trav(t,adj[x]) if (par[t] == 0) { par[t] = x; dfs(t); } } int need(int x, int y) { vi tri; trav(t,adj[x]) if (!inPath[t] && t != y) tri.pb(need(t,x)); sort(rall(tri)); int ans = 0; F0R(i,sz(tri)) ckmax(ans,i+1+tri[i]); return ans; } int get_max(int res, vi ans, vi path) { int cur = 0; F0R(i,sz(ans)) { if (ans[i]+cur > res) return i; if (ans[i]+cur < res) { cur ++; continue; } int x = ans[i]; vi tri; trav(t,adj[x]) if (!inPath[t]) tri.pb(need(t,x)); sort(rall(tri)); F0R(z,sz(tri)) tri[z] += 1+z; R0F(z,sz(tri)-1) ckmax(tri[z],tri[z+1]); int j = 0; while (j < sz(tri) && tri[0] == tri[j]) j ++, cur ++; cur ++; } return sz(ans); // dbg(ans,path); exit(0); } int main() { setIO(); re(N,A,B); // dbg(N,A,B); exit(0); F0R(i,N-1) { int x,y; re(x,y); adj[x].pb(y), adj[y].pb(x); } // dbg(N,A,B); exit(0); par[A] = -1; dfs(A); // FOR(i,1,N+1) dbg(i,par[i]); // exit(0); vi path = {B}; while (path.bk != A) path.pb(par[path.bk]); // dbg(path); trav(t,path) inPath[t] = 1; vi ans; trav(t,path) ans.pb(need(t,-1)); int res = 0; F0R(i,sz(ans)) ckmax(res,ans[i]+min(sz(ans)-1-i,i)+1); int max_pref = get_max(res-1,ans,path); reverse(all(path)); reverse(all(ans)); int max_pref_2 = get_max(res-1,ans,path); if (max_pref+max_pref_2 >= sz(path)) ps(res-1); else ps(res); // vi pref, suf; // { // int mx = 0, cnt = 0; // trav(t,ans) { // ckmax(mx,t+cnt); // pref.pb(mx); // cnt ++; // ckmax(mx,t+cnt); // } // } // reverse(all(ans)); // { // int mx = 0, cnt = 0; // trav(t,ans) { // ckmax(mx,t+cnt); // suf.pb(mx); // cnt ++; // ckmax(mx,t+cnt); // } // } // int res = MOD; // F0R(i,sz(path)-1) ckmin(res,max(pref[i],suf[sz(path)-2-i])); // ps(res); // 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 * DON'T GET STUCK ON ONE APPROACH */

Compilation message (stderr)

torrent.cpp: In function 'void setIn(str)':
torrent.cpp:182:28: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result]
  182 | void setIn(str s) { freopen(s.c_str(),"r",stdin); }
      |                     ~~~~~~~^~~~~~~~~~~~~~~~~~~~~
torrent.cpp: In function 'void setOut(str)':
torrent.cpp:183:29: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result]
  183 | void setOut(str s) { freopen(s.c_str(),"w",stdout); }
      |                      ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~
#Verdict Execution timeMemoryGrader output
Fetching results...
#Verdict Execution timeMemoryGrader output
Fetching results...