제출 #616918

#	제출 시각	아이디	문제	언어	결과	실행 시간	메모리
616918		nghiass001	One-Way Streets (CEOI17_oneway)	C++17	100 / 100	177 ms	37568 KiB

oneway

#include <bits/stdc++.h>
#define FOR(i, l, r) for(int i=(l); i<=(r); ++i)
#define REP(i, l, r) for(int i=(l); i<(r); ++i)
#define FORD(i, r, l) for(int i=(r); i>=(l); --i)
#define REPD(i, r, l)  for(int i=(r)-1; i>=(l); --i)
#define pii pair<int, int>
#define getbit(x, i) (((x) >> (i)) & 1)
using namespace std;
const int N = 1e5 + 5, M = 1e5 + 5, logN = 18, Qmax = 1e5 + 5;
int n, m, q, cnt, cnode, px[M], py[M];
int depth[N], p[N][logN], sedge[N], pre[N], parent_pair[Qmax];
int num[N], low[N], avail[N], exist[N], node[N];
vector<pii> S[N], Scc[N];
vector<int> Q, D[N], List;
char ans[M];

void Enter() {
    cin >> n >> m;
    FOR(i, 1, m) {
        int u, v;
        cin >> u >> v;
        S[u].emplace_back(v, i);
        S[v].emplace_back(u, -i);
    }
    cin >> q;
    FOR(i, 1, q) cin >> px[i] >> py[i];
}

void Tarjan(int u, int pre_edge) {
    num[u] = low[u] = ++cnt;
    Q.push_back(u);
    for(auto [v, c] : S[u]) if (-c != pre_edge) {
        if (num[v]) low[u] = min(low[u], num[v]);
        else {
            Tarjan(v, c);
            low[u] = min(low[u], low[v]);
        }
    }
    if (num[u] == low[u]) {
        ++cnode;
        int v;
        do {
            v = Q.back(); Q.pop_back();
            node[v] = cnode;
            D[cnode].push_back(v);
        } while (v != u);
    }
}

void Compress() {
    FOR(i, 1, n) if (!avail[i]) {
        Tarjan(i, 0);
    }
    FOR(i, 1, cnode) {
        exist[i] = i;
        for(int u : D[i]) for(auto [v, c] : S[u]) if (exist[node[v]] != i) {
            exist[node[v]] = i;
            Scc[i].emplace_back(node[v], c);
        }
    }
}

void DFS2(int u, int pa) {
    depth[u] = depth[pa] + 1;
    List.push_back(u);
    p[u][0] = pa;
    REP(i, 1, logN) p[u][i] = p[p[u][i - 1]][i - 1];

    for(auto [v, c] : Scc[u]) if (v != pa) {
        sedge[v] = c;
        DFS2(v, u);
    }
}

int LCA(int u, int v) {
    if (depth[u] > depth[v]) swap(u, v);
    int diff = depth[v] - depth[u];
    REPD(i, logN, 0) if (getbit(diff, i)) v = p[v][i];
    REPD(i, logN, 0) if (p[u][i] != p[v][i]) u = p[u][i], v = p[v][i];
    return (u == v ? u : p[u][0]);
}

void solve(char c1, char c2) {
    REPD(i, (int) List.size(), 0) {
        int u = List[i];
                assert(pre[u] >= 0);
        if (sedge[u] && pre[u]) {
            if (sedge[u] > 0) ans[sedge[u]] = c1;
            else ans[-sedge[u]] =  c2;
        }
        pre[p[u][0]] += pre[u];
    }
}

void Process() {
    Compress();
    FOR(i, 1, cnode) if (!depth[i]) DFS2(i, 0);

    FOR(i, 1, q) {
        int u = node[px[i]], v = node[py[i]];
        parent_pair[i] = LCA(u, v);
    }

    fill(ans + 1, ans + m + 1, 'B');
    FOR(i, 1, q) {
        int u = node[px[i]];
        ++pre[u]; --pre[parent_pair[i]];
    }
    solve('L', 'R');

    fill(pre + 1, pre + cnode + 1, 0);
    FOR(i, 1, q) {
        int u = node[py[i]];
        ++pre[u]; --pre[parent_pair[i]];
    }
    solve('R', 'L');

    cout << ans + 1;
}

int main()
{
    #define file "oneway"
    if (fopen(file".inp", "r")) {
        freopen(file".inp", "r", stdin);
        freopen(file".out", "w", stdout);
    }
    ios_base::sync_with_stdio(false);cin.tie(NULL);cout.tie(NULL);
    Enter();
    Process();
}

컴파일 시 표준 에러 (stderr) 메시지

oneway.cpp: In function 'int main()':
oneway.cpp:125:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  125 |         freopen(file".inp", "r", stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
oneway.cpp:126:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  126 |         freopen(file".out", "w", stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~

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