Submission #231481

#TimeUsernameProblemLanguageResultExecution timeMemory
231481rqiOne-Way Streets (CEOI17_oneway)C++14
100 / 100
231 ms36856 KiB
#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}; 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 bit(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 // 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 template<class A, class B> str ts(pair<A,B> p); template<class A> str ts(complex<A> c) { return ts(mp(c.real(),c.imag())); } str ts(bool b) { return b ? "true" : "false"; } str ts(char c) { str s = ""; s += c; return s; } str ts(str s) { return s; } str ts(const char* s) { return (str)s; } str ts(vector<bool> v) { bool fst = 1; str res = "{"; F0R(i,sz(v)) { if (!fst) res += ", "; fst = 0; res += ts(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 T> str ts(T v) { 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 << to_string(h); if (sizeof...(t)) cerr << ", "; DBG(t...); } #ifdef LOCAL // compile with -DLOCAL #define dbg(...) cerr << "[" << #__VA_ARGS__ << "]: [", DBG(__VA_ARGS__) #else #define dbg(...) 42 #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 } mt19937 rng((uint32_t)chrono::steady_clock::now().time_since_epoch().count()); /** * Description: Disjoint Set Union with path compression. * Add edges and test connectivity. Use for Kruskal'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-rank 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; } }; /**template<class T> T kruskal(int n, vector<pair<T,pi>> ed) { sort(all(ed)); T ans = 0; DSU D; D.init(n+1); // edges that unite are in MST trav(a,ed) if (D.unite(a.s.f,a.s.s)) ans += a.f; return ans; }*/ /** * Description: Calculates least common ancestor in tree * with root $R$ using binary jumping. * Time: O(N\log N) build, O(\log N) query * Source: USACO Camp * Verification: Debug the Bugs */ template<int SZ> struct LCA { static const int BITS = 32-__builtin_clz(SZ); int N = 1, par[BITS][SZ], depth[SZ], mind[SZ][2]; int ind[SZ]; //index of edge from i to par[i] vpi adj[SZ]; /// INITIALIZE void ae(int u, int v, int i) { adj[u].pb(mp(v, i)), adj[v].pb(mp(u, i)); } void dfs(int u, int prev, int index = 0){ ind[u] = index; par[0][u] = prev; depth[u] = depth[prev]+1; trav(v,adj[u]) if (v.f != prev) dfs(v.f, u, v.s); } void propmind(int node, int prv){ for(auto u: adj[node]){ if(u.f == prv) continue; propmind(u.f, node); for(int j = 0; j < 2; j++){ ckmin(mind[node][j], mind[u.f][j]); } } } void init(int _N) { N = _N; for(int i = 1; i <= N; i++){ //dbg(i); mind[i][0] = mind[i][1] = MOD; if(depth[i] == 0) dfs(i, 0); } FOR(k,1,BITS) FOR(i,1,N+1) par[k][i] = par[k-1][par[k-1][i]]; } /// QUERY int getPar(int a, int b) { R0F(k,BITS) if (b&(1<<k)) a = par[k][a]; return a; } int lca(int u, int v){ if (depth[u] < depth[v]) swap(u,v); u = getPar(u,depth[u]-depth[v]); R0F(k,BITS) if (par[k][u] != par[k][v]) u = par[k][u], v = par[k][v]; return u == v ? u : par[0][u]; } int dist(int u, int v) { return depth[u]+depth[v]-2*depth[lca(u,v)]; } }; const int mx = 100005; int n, m, p; pi elist[mx]; int dir[mx]; //0 = both, 1 = right, 2 = left vpi adj[mx]; pi cond[mx]; bool visited[mx]; bool processed[mx]; int dist[mx]; int mindepth[mx]; int par[mx]; vi child[mx]; DSU dsu; LCA<100105> lca; void genDFS(int node, int d = 0){ //dbg(node, d); visited[node] = 1; dist[node] = d; for(auto u: adj[node]){ if(processed[u.s] == 1) continue; processed[u.s] = 1; if(visited[u.f] == 1){ //backedge //dbg(node, u.f); ckmin(mindepth[node], dist[u.f]); continue; } child[node].pb(u.f); par[u.f] = node; genDFS(u.f, d+1); } } void propMinDepth(int node){ for(auto u: child[node]){ propMinDepth(u); ckmin(mindepth[node], mindepth[u]); } } int main() { setIO(); //#warning self & double edges? //Input cin >> n >> m; for(int i = 1; i <= m; i++){ int a, b; cin >> a >> b; elist[i] = mp(a, b); if(a == b) continue; //take care of self edges adj[a].pb(mp(b, i)); adj[b].pb(mp(a, i)); } int p; cin >> p; for(int i = 1; i <= p; i++){ int x, y; cin >> x >> y; cond[i] = mp(x, y); } //Generate dfs forest with depths & parent. When backedge occurs, put mindepth on that node. for(int i = 1; i <= n; i++) mindepth[i] = MOD; for(int i = 1; i <= n; i++){ if(visited[i] == 1) continue; genDFS(i); } //mindepth of every node becomes min of mindepth of all its children for(int i = 1; i <= n; i++){ if(dist[i] == 0) propMinDepth(i); } //for(int i = 1; i <= n; i++) dbg(i, mindepth[i]); //If mindepth < depth, merge and its parent in the DSU. dsu.init(n+5); for(int i = 1; i <= n; i++){ //dbg(i, par[i]); if(mindepth[i] < dist[i]){ //dbg(i, par[i]); dsu.unite(i, par[i]); } } //create LCA forest with new edges with dsu.get(), init. Probably change init for(int i = 1; i <= m; i++){ elist[i].f = dsu.get(elist[i].f); elist[i].s = dsu.get(elist[i].s); int a = elist[i].f; int b = elist[i].s; if(a != b){ lca.ae(a, b, i); //dbg(a, b, i); } } lca.init(n); //Upedges from a to lca, downedges from lca to b. //for(int i = 1; i <= n; i++) dbg(i, lca.depth[i]); for(int i = 1; i <= p; i++){ pi u = cond[i]; int a = dsu.get(u.f); int b = dsu.get(u.s); int c = lca.lca(a, b); //dbg(u, a, b, c); ckmin(lca.mind[a][0], lca.depth[c]); //up ckmin(lca.mind[b][1], lca.depth[c]); //down //dbg(a, c); //dbg(b, c); } //mindepth (for up & down) becomes min of mindepth for all its children for(int i = 1; i <= n; i++){ if(lca.depth[i] == 1){ lca.propmind(i, 0); } } //for(int i = 1; i <= n; i++) dbg(i, lca.mind[i][0], lca.mind[i][1]); //If mindepth < depth for up/down, direct the edge up/down. for(int i = 1; i <= n; i++){ int z = lca.ind[i]; if(z == 0) continue; for(int j = 0; j < 2; j++){ if(lca.mind[i][j] < lca.depth[i]){ int fac = 1; if(elist[z].f == i) fac = 0; //dbg(i, j, z, elist[z]); fac^=j; if(fac == 0){ dir[z] = 1; } else dir[z] = 2; /*if(elist[z].f == i){ //if j == 0, direct it right //if j == 1, direct it left } else{ //if j == 0, direct it left //if j == 1, direct it right }*/ } } } //Go through original edgelist and print for(int i = 1; i <= m; i++){ if(dir[i] == 0) cout << 'B'; else if(dir[i] == 1) cout << 'R'; else cout << 'L'; } cout << "\n"; // 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 (stderr)

oneway.cpp: In function 'void setIn(std::__cxx11::string)':
oneway.cpp:123:31: 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); }
                        ~~~~~~~^~~~~~~~~~~~~~~~~~~~~
oneway.cpp: In function 'void setOut(std::__cxx11::string)':
oneway.cpp:124:32: 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); }
                         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~
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