제출 #241067

#	제출 시각	아이디	문제	언어	결과	실행 시간	메모리
241067		osaaateiasavtnl	Railway Trip (JOI17_railway_trip)	C++14	30 / 100	2083 ms	11376 KiB

railway_trip

#include<bits/stdc++.h>
using namespace std;
#define ii pair <int, int>
#define app push_back
#define all(a) a.begin(), a.end()
#define bp __builtin_popcountll
#define ll long long
#define mp make_pair
#define f first
#define s second
#define Time (double)clock()/CLOCKS_PER_SEC
 
const int N = 1e5+7, INF = 1e9+7;
int n, k, q;
int a[N], ans[N];
int pref[N], suff[N];
int newl[N], newr[N];
vector <int> pos[N];

int par[N];
int root(int u) {
    if (par[u] == u)
        return u;
    else
        return par[u] = root(par[u]);
}
void merge(int u, int v) {
    u = root(u);
    v = root(v);
    if (u != v) {
        par[u] = v;
    }
}   

int link_l[N], link_r[N];

signed main() {
    #ifdef HOME
    freopen("input.txt", "r", stdin);
    #else
    #define endl '\n'
    ios_base::sync_with_stdio(0); cin.tie(0);
    #endif
    cin >> n >> k >> q; 
    for (int i = 1; i <= n; ++i)
        cin >> a[i];
 
    vector <ii> d;
    for (int i = 0; i < q; ++i) {
        int u, v;
        cin >> u >> v;
        if (v < u)
            swap(u, v);
        d.app(mp(u, v));            
        ans[i] = INF;
    }   

    for (int i = 1; i <= k; ++i)
        pos[i].app(0);    
    for (int i = 1; i <= n; ++i)
        pos[a[i]].app(i);
    for (int i = 1; i <= k; ++i)
        pos[i].app(n+1);

    for (int i = 1; i <= n; ++i)
        par[i] = i;

    auto same_dist = [&](int i, int j) {
        int p1 = lower_bound(all(pos[a[i]]), i) - pos[a[i]].begin();
        int p2 = lower_bound(all(pos[a[j]]), j) - pos[a[j]].begin();
        return abs(p1-p2);
    };

    for (int x = 1; x <= k; ++x) {
        //cout << "x " << x << endl;

        for (int i : pos[x]) {
            if (i && a[i - 1] <= x) {
                merge(i, i - 1);
            }   
            if (i + 1 <= n && a[i + 1] <= x) {
                merge(i, i + 1);
            }   
        }

        memset(link_l, 0, sizeof link_l);
        memset(link_r, 0, sizeof link_r);
        for (int i = 1; i <= n; ++i)
            newl[i] = newr[i] = INF;

        for (int i : pos[x]) {
            link_l[i] = link_r[i] = i;
            newl[i] = newr[i] = 0;
            for (int j = i - 1; j; --j) {
                if (a[j] >= a[i])
                    break;
                newr[j] = suff[j]+1;
                link_r[j] = i;
            }   
            for (int j = i + 1; j <= n; ++j) {
                if (a[j] >= a[i])
                    break;
                newl[j] = pref[j]+1;
                link_l[j] = i;
            }
        }   

        for (int i = 1; i <= n; ++i) {
            newl[i] = min(newl[i], newr[i]+1);
            newr[i] = min(newr[i], newl[i]+1);
        }   
        
        //pref - dist to nearest prefix maximum
        //suff - dist to nearest suffix maximum
        //newl - dist to nearest left x
        //newr - dist to nearest right x
        //link_l = number of the nearest left x

        int lf = 0;
        for (int i = 1; i <= n; ++i) {
            if (a[i] > x) {
                lf = i;
                continue;
            }
            auto t = upper_bound(all(pos[x]), lf);
            if (*t <= i) {
                auto link = prev(upper_bound(all(pos[x]), i));
                pref[i] = newl[i] + (link - t);
            }   
            else if (link_r[i]) {
                pref[i] = min(pref[i], newr[i]);
            }   
        }   

        int rf = n+1;
        for (int i = n; i; --i) {
            if (a[i] > x) {
                rf = i;
                continue;
            }   
            auto t = prev(upper_bound(all(pos[x]), rf));
            if (*t >= i) {
                auto link = lower_bound(all(pos[x]), i);
                suff[i] = newr[i] + (t - link);
            }   
            else if (link_l[i]) {
                suff[i] = min(suff[i], newl[i]);
            }   
        }   

        for (int i = 0; i < q; ++i) {
            int u = d[i].f, v = d[i].s;
            if (root(u) == root(v)) {
                if (link_l[u] && link_l[v]) {
                    ans[i] = min(ans[i], newl[u] + newl[v] + same_dist(link_l[u], link_l[v]));
                }
                if (link_l[u] && link_r[v]) {
                    ans[i] = min(ans[i], newl[u] + newr[v] + same_dist(link_l[u], link_r[v]));
                }
                if (link_r[u] && link_l[v]) {
                    ans[i] = min(ans[i], newr[u] + newl[v] + same_dist(link_r[u], link_l[v]));
                }
                if (link_r[u] && link_r[v]) {
                    ans[i] = min(ans[i], newr[u] + newr[v] + same_dist(link_r[u], link_r[v]));
                }
            }
        }   
    }       

    for (int i = 0; i < q; ++i)
        cout << ans[i] - 1 << endl;
}

• Subtask 1: 5 / 5
• Subtask 2: 0 / 15
• Subtask 3: 25 / 25
• Subtask 4: 0 / 55