Submission #1533457

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Source Code Expand

#include "bits/stdc++.h"
using namespace std;
#define FOR(i,j,k) for(int (i)=(j);(i)<(int)(k);++(i))
#define rep(i,j) FOR(i,0,j)
#define each(x,y) for(auto &(x):(y))
#define mp make_pair
#define MT make_tuple
#define all(x) (x).begin(),(x).end()
#define debug(x) cout<<#x<<": "<<(x)<<endl
#define smax(x,y) (x)=max((x),(y))
#define smin(x,y) (x)=min((x),(y))
#define MEM(x,y) memset((x),(y),sizeof (x))
#define sz(x) (int)(x).size()
#define rt return
using dbl = double;
using ll = long long;
using pii = pair<int, int>;
using vi = vector<int>;
using vll = vector<ll>;

/*
セグメント木を利用したRMQ
初期化 O(N)
クエリ O(log(N))

*/
template<class Val, class Cmp>
class DynamicRMQ {
    int n;
    Val init;
    vector<Val> dat;
    Cmp cmp;
    inline Val query(int a, int b, int k, int l, int r) {
        if (r <= a || b <= l) return init;
        if (a <= l&&r <= b) return dat[k];
        else {
            Val vl, vr;
            vl = query(a, b, k << 1, l, (l + r) >> 1);
            vr = query(a, b, (k << 1) | 1, (l + r) >> 1, r);
            return cmp(vl, vr) ? vl : vr;
        }
    }
public:
    DynamicRMQ() {}
    DynamicRMQ(int n_, Val init_) :n(1), init(init_) {
        for (; n<n_; n <<= 1);
        dat = vector<Val>(n << 1, init);
    }
    void update(int k, Val a) {
        k += n;
        dat[k] = a;
        while (k > 1) {
            k >>= 1;
            dat[k] = cmp(dat[k << 1], dat[(k << 1) | 1]) ? dat[k << 1] : dat[(k << 1) | 1];
        }
    }
    Val query(int a, int b) {
        return query(a, b, 1, 0, n);
    }
};

int main(){
    ios::sync_with_stdio(false);
    cin.tie(0);

    int N, INF = 1 << 30;
    cin >> N;
    vi P(N), A(N + 1);
    rep(i, N) {
        cin >> P[i];
        A[P[i]] = i;
    }

    using RMQ = DynamicRMQ<pii, less<pii> >;
    using T = tuple<pii, int, int>;
    RMQ rmq[2];
    rep(i, 2)rmq[i] = RMQ(N, mp(INF,i));
    rep(i, N)rmq[i&1].update(i, mp(P[i],i));

    priority_queue<T, vector<T>, greater<T> > Q;
    Q.push(T(rmq[0].query(0, N), 0, N));
    vi ans;
    
    auto f = [&](int l, int r) {
        if (l >= r)return;
        pii p = rmq[l&1].query(l, r);
        Q.push(T(p, l, r));
        return;
    };

    while (sz(Q)) {
        pii p;
        int x, m, l, r;
        tie(p, l, r) = Q.top();
        Q.pop();
        tie(x, m) = p;
        // l=<m<n<r
        int y, n;
        tie(y, n) = rmq[!(l&1)].query(m + 1, r);
        ans.push_back(x);
        ans.push_back(y);
        rmq[0].update(m, mp(INF, m));
        rmq[1].update(n, mp(INF, n));
        f(l, m);
        f(m+1, n);
        f(n + 1, r);
    }

    rep(i, N)cout << ans[i] << (i != N - 1 ? ' ' : '\n');
}

Submission Info

Judge Result