結果

問題 No.274 The Wall
ユーザー yuji9511
提出日時 2020-12-24 13:03:54
言語 C++17
(gcc 13.3.0 + boost 1.87.0)
結果
AC  
実行時間 1,138 ms / 2,000 ms
コード長 4,777 bytes
コンパイル時間 2,872 ms
コンパイル使用メモリ 209,516 KB
最終ジャッジ日時 2025-01-17 06:39:37
ジャッジサーバーID
（参考情報） 		judge1 / judge3
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ファイルパターン 結果
sample AC * 4
other AC * 22
権限があれば一括ダウンロードができます

ソースコード

diff #
プレゼンテーションモードにする

/*** author: yuji9511 ***/
#include <bits/stdc++.h>
// #include <atcoder/all>
// using namespace atcoder;
using namespace std;
using ll = long long;
using lpair = pair<ll, ll>;
using vll = vector<ll>;
const ll MOD = 1e9+7;
const ll INF = 1e18;
#define rep(i,m,n) for(ll i=(m);i<(n);i++)
#define rrep(i,m,n) for(ll i=(m);i>=(n);i--)
#define printa(x,n) for(ll i=0;i<n;i++){cout<<(x[i])<<" \n"[i==n-1];};
void print() {}
template <class H,class... T>
void print(H&& h, T&&... t){cout<<h<<" \n"[sizeof...(t)==0];print(forward<T>(t)...);}
template <class E> struct csr {
    std::vector<int> start;
    std::vector<E> elist;
    csr(int n, const std::vector<std::pair<int, E>>& edges)
        : start(n + 1), elist(edges.size()) {
        for (auto e : edges) {
            start[e.first + 1]++;
        }
        for (int i = 1; i <= n; i++) {
            start[i] += start[i - 1];
        }
        auto counter = start;
        for (auto e : edges) {
            elist[counter[e.first]++] = e.second;
        }
    }
};
// Reference:
// R. Tarjan,
// Depth-First Search and Linear Graph Algorithms
struct scc_graph {
  public:
    scc_graph(int n) : _n(n) {}
    int num_vertices() { return _n; }
    void add_edge(int from, int to) { edges.push_back({from, {to}}); }
    // @return pair of (# of scc, scc id)
    std::pair<int, std::vector<int>> scc_ids() {
        auto g = csr<edge>(_n, edges);
        int now_ord = 0, group_num = 0;
        std::vector<int> visited, low(_n), ord(_n, -1), ids(_n);
        visited.reserve(_n);
        auto dfs = [&](auto self, int v) -> void {
            low[v] = ord[v] = now_ord++;
            visited.push_back(v);
            for (int i = g.start[v]; i < g.start[v + 1]; i++) {
                auto to = g.elist[i].to;
                if (ord[to] == -1) {
                    self(self, to);
                    low[v] = std::min(low[v], low[to]);
                } else {
                    low[v] = std::min(low[v], ord[to]);
                }
            }
            if (low[v] == ord[v]) {
                while (true) {
                    int u = visited.back();
                    visited.pop_back();
                    ord[u] = _n;
                    ids[u] = group_num;
                    if (u == v) break;
                }
                group_num++;
            }
        };
        for (int i = 0; i < _n; i++) {
            if (ord[i] == -1) dfs(dfs, i);
        }
        for (auto& x : ids) {
            x = group_num - 1 - x;
        }
        return {group_num, ids};
    }
    std::vector<std::vector<int>> scc() {
        auto ids = scc_ids();
        int group_num = ids.first;
        std::vector<int> counts(group_num);
        for (auto x : ids.second) counts[x]++;
        std::vector<std::vector<int>> groups(ids.first);
        for (int i = 0; i < group_num; i++) {
            groups[i].reserve(counts[i]);
        }
        for (int i = 0; i < _n; i++) {
            groups[ids.second[i]].push_back(i);
        }
        return groups;
    }
  private:
    int _n;
    struct edge {
        int to;
    };
    std::vector<std::pair<int, edge>> edges;
};
struct two_sat {
  public:
    two_sat() : _n(0), scc(0) {}
    two_sat(int n) : _n(n), _answer(n), scc(2 * n) {}
    void add_clause(int i, bool f, int j, bool g) {
        assert(0 <= i && i < _n);
        assert(0 <= j && j < _n);
        scc.add_edge(2 * i + (f ? 0 : 1), 2 * j + (g ? 1 : 0));
        scc.add_edge(2 * j + (g ? 0 : 1), 2 * i + (f ? 1 : 0));
    }
    bool satisfiable() {
        auto id = scc.scc_ids().second;
        for (int i = 0; i < _n; i++) {
            if (id[2 * i] == id[2 * i + 1]) return false;
            _answer[i] = id[2 * i] < id[2 * i + 1];
        }
        return true;
    }
    std::vector<bool> answer() { return _answer; }
  private:
    int _n;
    std::vector<bool> _answer;
    scc_graph scc;
};
void solve(){
    ll N,M;
    cin >> N >> M;
    vll L(N), R(N);
    rep(i,0,N) cin >> L[i] >> R[i];
    two_sat ts(N);
    rep(i,0,N){
        rep(j,0,N){
            if(i == j) continue;
            if(max(L[i], L[j]) <= min(R[i], R[j])){
                ts.add_clause(i, false, j, false);
            }
            if(max(L[i], M-1-R[j]) <= min(R[i], M-1-L[j])){
                ts.add_clause(i, false, j, true);
            }
            if(max(M-1-R[i], L[j]) <= min(M-1-L[i], R[j])){
                ts.add_clause(i, true, j, false);
            }
            if(max(M-1-R[i], M-1-R[j]) <= min(M-1-L[i], M-1-L[j])){
                ts.add_clause(i, true, j, true);
            }
        }
    }
    bool ok = ts.satisfiable();
    if(ok){
        print("YES");
    }else{
        print("NO");
    }
}
int main(){
    cin.tie(0);
    ios::sync_with_stdio(false);
    solve();
}
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