#941113 (C++17) No.2543 Many Meetings

• 問題: No.2543 Many Meetings
• ユーザー: kwm_t
• 提出日時: 2023-12-30 01:22:54
• 言語: C++17 (gcc 13.3.0 + boost 1.87.0)
• 結果: WA
• 実行時間: -
• コード長: 2,827 bytes
• コンパイル時間: 2,429 ms
• コンパイル使用メモリ: 207,880 KB
• 最終ジャッジ日時: 2025-02-18 15:22:56
• ジャッジサーバーID （参考情報）: judge4 / judge1

ファイルパターン	結果
sample	AC * 3
other	AC * 30 WA * 10

ソースコード

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#include <bits/stdc++.h>
//#include <atcoder/all>
using namespace std;
//using namespace atcoder;
//using mint = modint998244353;
//const int mod = 998244353;
//using mint = modint1000000007;
//const int mod = 1000000007;
const int INF = 1e9;
//const long long LINF = 1e18;
#define rep(i, n) for (int i = 0; i < (n); ++i)
#define rep2(i,l,r)for(int i=(l);i<(r);++i)
#define rrep(i, n) for (int i = (n-1); i >= 0; --i)
#define rrep2(i,l,r)for(int i=(r-1);i>=(l);--i)
#define all(x) (x).begin(),(x).end()
#define allR(x) (x).rbegin(),(x).rend()
#define P pair<int,int>
template<typename A, typename B> inline bool chmax(A & a, const B & b) { if (a < b) { a = b; return true; } return false; }
template<typename A, typename B> inline bool chmin(A & a, const B & b) { if (a > b) { a = b; return true; } return false; }
bool chk(const vector<P> &v, int k) {
    int pre = 0;
    int cnt = 0;
    rep2(i, 1, v.size()) {
        if (v[pre].second <= v[i].first) {
            cnt++;
            pre = i;
        }
    }
    return cnt >= k;
}
int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    int n, k; cin >> n >> k;
    vector<P>d(n);
    rep(i, n)cin >> d[i].first >> d[i].second;
    sort(all(d), [](const P x, const P &y) {return x.second < y.second; });
    if (!chk(d, k)) {
        cout << -1 << endl;
        return 0;
    }
    vector<int>next(n, -1);// todo 高速化
    {
        struct SubD {
            int l, r, idx;
            SubD() {};
            SubD(int l, int r, int idx) : l(l), r(r), idx(idx) {};
        };
        vector<SubD>subD(n);
        rep(i, n) {
            subD[i] = SubD(d[i].first, d[i].second, i);
        }
        int mn = INF;
        int idx = -1;
        sort(all(subD), [](const SubD x, const SubD &y) {return x.l < y.l; });
        rrep(i, n) {
            while (!subD.empty() && d[i].second <= subD.back().l) {
                auto top = subD.back();
                if (chmin(mn, top.r))idx = top.idx;
                subD.pop_back();
            }
            next[i] = idx;
        }
    }
    /*rep(i, n) {
        rep(j, n) {
            if (d[i].second > d[j].first)continue;
            if (-1 == next[i])next[i] = j;
            else if (d[j].second < d[next[i]].second)next[i] = j;
        }
    }*/
    // dp[i][j]:=iから初めて2^j個数選ぶ時の最後に選んだindex
    vector dp(n, vector<int>(20, -1));
    rep(i, n)dp[i][0] = i;
    rep2(i, 1, 20) {
        rep(j, n) {
            int x0 = dp[j][i - 1];
            if (-1 == x0)continue;
            int x1 = next[x0];
            if (-1 == x1)continue;
            int x2 = dp[x1][i - 1];
            dp[j][i] = x2;
        }
    }
    int ans = INF;
    rep(i, n) {
        int ck = k;
        int ci = i;
        bool chk = true;
        rep(j, 20) {
            if (1 == ck % 2) {
                if (i != ci)ci = next[ci];
                if (-1 == ci) {
                    chk = false;
                    break;
                }
                ci = dp[ci][j];
                if (-1 == ci) {
                    chk = false;
                    break;
                }
            }
            ck /= 2;
        }
        if (chk) {
            int val = d[ci].second - d[i].first;
            chmin(ans, val);
            //cout << i << " " << ci << endl;
        }
    }
    /*rep(i, n) {
        rep(j, 5) {
            cout << dp[i][j] << " ";
        }cout << endl;
    }*/
    cout << ans << endl;
    return 0;
}
 
 
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