Submission #644273

#	Time	Username	Problem	Language	Result	Execution time	Memory
644273		farmerboy	One-Way Streets (CEOI17_oneway)	C++17	100 / 100	183 ms	45364 KiB

oneway

/*
    Template Version: 1.0.0 - 20220620
    Author: Nguyen Tan Bao
    Status:
    Idea:
*/

#include <bits/stdc++.h>
#define FI first
#define SE second
#define ALL(a) a.begin(), a.end()
#define SZ(a) int((a).size())
#define MS(s, n) memset(s, n, sizeof(s))
#define FOR(i,a,b) for (int i = (a); i <= (b); i++)
#define FORE(i,a,b) for (int i = (a); i >= (b); i--)
#define FORALL(it, a) for (__typeof((a).begin()) it = (a).begin(); it != (a).end(); it++)
#define TRAV(x, a) for (auto &x : a)

using namespace std;
using ll = long long; using ld = double; 
using pi = pair<int, int>; using pl = pair<ll, ll>; using pd = pair<ld, ld>;
using cd = complex<ld>; using vcd = vector<cd>;

using vi = vector<int>; using vl = vector<ll>;
using vd = vector<ld>; using vs = vector<string>;
using vpi = vector<pi>; using vpl = vector<pl>; using vpd = vector<pd>; // vector<pair>

template<class T> using min_pq = priority_queue<T, vector<T>, greater<T> >;
template<class T> inline int ckmin(T& a, const T& val) { return val < a ? a = val, 1 : 0; }
template<class T> inline int ckmax(T& a, const T& val) { return a < val ? a = val, 1 : 0; }
template<class T> void remDup(vector<T>& v) { sort(ALL(v)); v.erase(unique(ALL(v)), end(v)); }

constexpr int pct(int x) { return __builtin_popcount(x); } // # of bits set
constexpr int bits(int x) { return x == 0 ? 0 : 31-__builtin_clz(x); } // floor(log2(x)) 
constexpr int p2(int x) { return 1<<x; }
constexpr int msk2(int x) { return p2(x)-1; }

ll ceilDiv(ll a, ll b) { return a / b + ((a ^ b) > 0 && a % b); } // divide a by b rounded up
ll floorDiv(ll a, ll b) { return a / b - ((a ^ b) < 0 && a % b); } // divide a by b rounded down
void setPrec(int x) { cout << fixed << setprecision(x); }

// TO_STRING
#define ts to_string
string ts(char c) { return string(1, c); }
string ts(const char* s) { return (string) s; }
string ts(string s) { return s; }
string ts(bool b) { return (b ? "true" : "false"); }

template<class T> using V = vector<T>;
template<class T> string ts(complex<T> c);
string ts(V<bool> v);
template<size_t sz> string ts(bitset<sz> b);
template<class T> string ts(T v);
template<class T, class U> string ts(pair<T,U> p);
template<class ...U> string ts(tuple<U...> u);

template<class T> string ts(complex<T> c) { stringstream ss; ss << c; return ss.str(); }
string ts(V<bool> v) {string res = "{"; FOR(i,0,SZ(v)-1) res += char('0'+v[i]); res += "}"; return res; }
template<size_t sz> string ts(bitset<sz> b) { string res = ""; FOR(i,0,SZ(b)-1) res += char('0'+b[i]); return res; }
template<class T> string ts(T v) { // containers with begin(), end()
    bool fst = 1; string res = "";
    for (const auto& x: v) { if (!fst) res += " "; fst = 0; res += ts(x); }
    return res;
}
template<class T, class U> string ts(pair<T,U> p) { return "(" + ts(p.FI) + ", " + ts(p.SE) + ")"; }
template<size_t i, class T> string print_tuple_utils(const T& tup) { if constexpr(i == tuple_size<T>::value) return ")"; else return (i ? ", " : "(") + ts(get<i>(tup)) + print_tuple_utils<i + 1, T>(tup); }
template<class ...U> string ts(tuple<U...> u) { return print_tuple_utils<0, tuple<U...>>(u); }

// OUTPUT
template<class T> void pr(T x) { cout << ts(x); }
template<class T, class ...U> void pr(const T& t, const U&... u) { pr(t); pr(u...); }
void ps() { pr("\n"); } // print w/ spaces
template<class T, class ...U> void ps(const T& t, const U&... u) { pr(t); if (sizeof...(u)) pr(" "); ps(u...); }

// DEBUG
void DBG() { cerr << "]" << endl; }
template<class T, class ...U> void DBG(const T& t, const U&... u) { cerr << ts(t); if (sizeof...(u)) cerr << ", "; DBG(u...); }

#ifdef LOCAL_DEBUG
#define CONCAT(x, y) x##y
#define with_level setw(__db_level * 2) << setfill(' ') << "" << setw(0)
#define dbg(...) cerr << with_level << "Line(" << __LINE__ << ") -> [" << #__VA_ARGS__ << "]: [", DBG(__VA_ARGS__)
#define chk(...) if (!(__VA_ARGS__)) cerr << setw(__db_level * 2) << setfill(' ') << "" << setw(0) << "Line(" << __LINE__ << ") -> function(" << __FUNCTION__  << ") -> CHK FAILED: (" << #__VA_ARGS__ << ")" << "\n", exit(0);
#define db_block() debug_block CONCAT(dbbl, __LINE__)
int __db_level = 0;
struct debug_block {
    debug_block() { cerr << with_level << "{" << endl; ++__db_level; }
    ~debug_block() { --__db_level; cerr << with_level << "}" << endl; }
};
#else
#define dbg(...) 0
#define chk(...) 0
#define db_block() 0
#endif

const ld PI = acos(-1.0);
const int dx[4] = {1,0,-1,0}, dy[4] = {0,1,0,-1};
const ld EPS = 1e-9;
const ll MODBASE = 1000000007LL;
const int INF = 0x3f3f3f3f;

const int MAXN = 100010;
const int MAXM = 1000;
const int MAXK = 16;
const int MAXQ = 200010;

int n, m, level[MAXN], dp[MAXN], par[MAXN], cnt[MAXN];
int res[MAXN], newIdx[MAXN], N;
vector<vi> a[MAXN], b[MAXN], edges2;
vpi edges;
bool visited[MAXN];

void dfs(int u, int p, int edgeIdx) {
    TRAV(pa, a[u]) {
        int v = pa[0];
        int idx = pa[1];
        int dir = pa[2];
        if (!level[v]) {
            level[v] = level[u] + 1;
            res[idx] = dir;
            dfs(v, u, idx);
            dp[u] += dp[v];
        } else {
            if (idx == edgeIdx) continue;
            res[idx] = 2;
            if (level[v] > level[u]) {
                // going down
                dp[u]--;
            } else {
                // going up
                dp[u]++;
            }
        }
    }

    if (p != 0 && dp[u] == 0) {
        res[edgeIdx] = -1;
    } else {
        res[edgeIdx] = 2;
    }
}

void dfs2(int u, int group) {
    newIdx[u] = group;
    TRAV(pa, a[u]) {
        int v = pa[0];
        int idx = pa[1];
        int dir = pa[2];
        if (res[idx] != 2) {
            continue;
        }
        if (!newIdx[v]) {
            dfs2(v, group);
        }
    }
}

void dfs3(int u, int h) {
    visited[u] = 1;
    TRAV(pa, b[u]) {
        int v = pa[0];
        int idx = pa[1];
        int dir = pa[2];
        if (!visited[v]) {
            par[v] = u;
            dfs3(v, h);
            cnt[u] += cnt[v];
        }
    }
}

int main() {
    ios::sync_with_stdio(0);
    cin.tie(nullptr);
    cin >> n >> m;
    FOR(i,1,m) {
        int u, v;
        cin >> u >> v;
        a[u].push_back({v, i, 1});
        a[v].push_back({u, i, 0});
        edges.push_back({u, v});
        res[i] = ' ';
    }

    FOR(i,1,n) {
        if (!level[i]) {
            level[i] = 1;
            dfs(i, 0, -1);
        }
    }

    FOR(i,1,n)
        if (!newIdx[i]) {
            N++;
            dfs2(i, N);
        }
    
    FOR(i,0,m-1) {
        int u = edges[i].FI, v = edges[i].SE, cs = i + 1;
        u = newIdx[u];
        v = newIdx[v];
        if (u != v) {
            b[u].push_back({v, cs, 1});
            b[v].push_back({u, cs, 0});
            edges2.push_back({u, v, cs});
        }
    }

    int q;
    cin >> q;
    while (q--) {
        int u, v;
        cin >> u >> v;
        u = newIdx[u];
        v = newIdx[v];
        if (u != v) {
            cnt[u]++;
            cnt[v]--;
        }
    }

    FOR(i,1,N) {
        if (!visited[i]) {
            dfs3(i, i);
        }
    }

    FOR(i,0,SZ(edges2)-1) {
        int u = edges2[i][0], v = edges2[i][1], c = edges2[i][2];
        if (par[u] == v) {
            int l = cnt[u], r = -cnt[u];
            if (l < 0) {
                res[c] = 0;
            } else if (r < 0) {
                res[c] = 1;
            } else {
                res[c] = 2;
            }
        } else {
            int l = cnt[v], r = -cnt[v];
            if (l < 0) {
                res[c] = 1;
            } else if (r < 0) {
                res[c] = 0;
            } else {
                res[c] = 2;
            }
        }
    }

    FOR(i,1,m) {
        if (res[i] == 2) cout << 'B';
        else if (res[i] == 1) cout << 'R';
        else cout << 'L';
    }
    return 0;
}

Compilation message (stderr)

oneway.cpp: In function 'void dfs2(int, int)':
oneway.cpp:148:13: warning: unused variable 'dir' [-Wunused-variable]
  148 |         int dir = pa[2];
      |             ^~~
oneway.cpp: In function 'void dfs3(int, int)':
oneway.cpp:162:13: warning: unused variable 'idx' [-Wunused-variable]
  162 |         int idx = pa[1];
      |             ^~~
oneway.cpp:163:13: warning: unused variable 'dir' [-Wunused-variable]
  163 |         int dir = pa[2];
      |             ^~~

• Subtask 1: 30 / 30
• Subtask 2: 30 / 30
• Subtask 3: 40 / 40