Submission #335430

#	Time	Username	Problem	Language	Result	Execution time	Memory
335430		ec1117	Pipes (CEOI15_pipes)	C++17	20 / 100	1032 ms	65540 KiB

pipes

#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<pi, int> pii;
typedef pair<ll,ll> pl; 
typedef pair<db,db> pd; 

typedef vector<int> vi; 
typedef vector<bool> vb; 
typedef vector<ll> vl; 
typedef vector<db> vd; 
typedef vector<str> vs; 
typedef vector<pi> vpi;
typedef vector<pl> vpl; 
typedef vector<pd> vpd; 
template<class T> using V = vector<T>; 
template<class T, size_t SZ> using AR = array<T,SZ>; 

#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 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 

#define FOR(i,a,b) for (int i = (a); i < (b); ++i)
#define F0R(i,a) FOR(i,0,a)
#define For(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 Rof(i,a) ROF(i,0,a)
#define trav(a,x) for (auto& a: x)

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; } 
constexpr int pct(int x) { return __builtin_popcount(x); } 
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
ll half(ll x) { return fdiv(x,2); }

template<class T, class U> T fstTrue(T lo, T hi, U f) { 
        // note: if (lo+hi)/2 is used instead of half(lo+hi) then this will loop infinitely when lo=hi
        hi ++; assert(lo <= hi); // assuming f is increasing
        while (lo < hi) { // find first index such that f is true 
                T mid = half(lo+hi);
                f(mid) ? hi = mid : lo = mid+1; 
        } 
        return lo;
}
template<class T, class U> 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 = half(lo+hi+1);
                f(mid) ? lo = mid : hi = mid-1;
        } 
        return lo;
}
template<class T> void remDup(vector<T>& v) { 
        sort(all(v)); v.erase(unique(all(v)),end(v)); }

// 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(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
}
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()
        #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
}
template<class A, class B> str ts(pair<A,B> p) {
        #ifdef LOCAL
                return "("+ts(p.f)+", "+ts(p.s)+")"; 
        #else
                return ts(p.f)+" "+ts(p.s);
        #endif
}

// 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, 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

int gcd(int a, int b) {if (b == 0)return a;return gcd(b, a % b);}
int max(int a,int b, int c){return max(a,max(b,c));}
int min(int a,int b, int c){return min(a,min(b,c));}
ll max(ll a,ll b, ll c){return max(a,max(b,c));}
ll min(ll a,ll b, ll c){return min(a,min(b,c));}
void dbga(int arr[], int n){vi v;For(i,n)v.pb(arr[i]);dbg(v);}
void dbga(ll arr[], int n){vi v;For(i,n)v.pb(arr[i]);dbg(v);}

// 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
}
// 576743 29995400689069LL
const int MOD = 1e9+7; // 998244353;
const int MX = 3e5+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());

/**
 * Description: Biconnected components of edges. Removing any vertex in BCC
    * doesn't disconnect it. To get block-cut tree, create a bipartite graph
    * with the original vertices on the left and a vertex for each BCC on the right. 
    * Draw edge $u\leftrightarrow v$ if $u$ is contained within the BCC for $v$.
    * Self-loops are not included in any BCC while BCCS of size 1 represent
    * bridges.
 * Time: O(N+M)
 * Source: GeeksForGeeks (corrected)
 * Verification: 
    * USACO December 2017, Push a Box -> https://pastebin.com/yUWuzTH8
    * https://cses.fi/problemset/task/1705/
 */

struct BCC {
    vector<vpi> adj; vpi ed; 
    vector<vi> comps; // edges for each bcc
    int N, ti = 0; vi disc, st; 
    void init(int _N) { N = _N; disc.rsz(N), adj.rsz(N); }
    void ae(int x, int y) { 
        adj[x].eb(y,sz(ed)), adj[y].eb(x,sz(ed)), ed.eb(x,y); }
    int dfs(int x, int p = -1) { // return lowest disc
        int low = disc[x] = ++ti;
        trav(e,adj[x]) if (e.s != p) {
            if (!disc[e.f]) {
                st.pb(e.s); // disc[x] < LOW -> bridge
                int LOW = dfs(e.f,e.s); ckmin(low,LOW); 
                if (disc[x] <= LOW) { // get edges in bcc
                    comps.eb(); vi& tmp = comps.bk; // new bcc
                    for (int y = -1; y != e.s; )
                        tmp.pb(y = st.bk), st.pop_back();
                }
            } else if (disc[e.f] < disc[x]) // back-edge
                ckmin(low,disc[e.f]), st.pb(e.s);
        }
        return low;
    }
    void gen() { F0R(i,N) if (!disc[i]) dfs(i);  }
};

BCC bcc;
void solve(){
    int n,m;re(n,m);
    bcc.init(n);
    For(i,m){
        int a,b;re(a,b);a--;b--;
        bcc.ae(a,b);
    }
    bcc.gen();
    trav(x,bcc.comps){
        dbg(x);
        if(sz(x)==1){
            ps(bcc.ed[x[0]].f+1,bcc.ed[x[0]].s+1);
        }
    }
}

int main() {
        setIO();
        int t=1;
        // re(t);
        while(t--)solve();
        // 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)

pipes.cpp: In function 'void dbga(int*, int)':
pipes.cpp:162:26: warning: statement has no effect [-Wunused-value]
  162 |         #define dbg(...) 0
      |                          ^
pipes.cpp:171:55: note: in expansion of macro 'dbg'
  171 | void dbga(int arr[], int n){vi v;For(i,n)v.pb(arr[i]);dbg(v);}
      |                                                       ^~~
pipes.cpp: In function 'void dbga(ll*, int)':
pipes.cpp:162:26: warning: statement has no effect [-Wunused-value]
  162 |         #define dbg(...) 0
      |                          ^
pipes.cpp:172:54: note: in expansion of macro 'dbg'
  172 | void dbga(ll arr[], int n){vi v;For(i,n)v.pb(arr[i]);dbg(v);}
      |                                                      ^~~
pipes.cpp: In function 'void solve()':
pipes.cpp:162:26: warning: statement has no effect [-Wunused-value]
  162 |         #define dbg(...) 0
      |                          ^
pipes.cpp:243:9: note: in expansion of macro 'dbg'
  243 |         dbg(x);
      |         ^~~
pipes.cpp: In function 'void setIn(str)':
pipes.cpp:175:28: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result]
  175 | void setIn(str s) { freopen(s.c_str(),"r",stdin); }
      |                     ~~~~~~~^~~~~~~~~~~~~~~~~~~~~
pipes.cpp: In function 'void setOut(str)':
pipes.cpp:176:29: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result]
  176 | void setOut(str s) { freopen(s.c_str(),"w",stdout); }
      |                      ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 10 / 10
• Subtask 2: 10 / 10
• Subtask 3: 0 / 10
• Subtask 4: 0 / 10
• Subtask 5: 0 / 10
• Subtask 6: 0 / 10
• Subtask 7: 0 / 10
• Subtask 8: 0 / 10
• Subtask 9: 0 / 10
• Subtask 10: 0 / 10