Submission #712015

#	Time	Username	Problem	Language	Result	Execution time	Memory
712015		Lobo	Valley (BOI19_valley)	C++17	100 / 100	234 ms	36564 KiB

valley

#include<bits/stdc++.h>
using namespace std;
const long long inf = (long long) 1e18 + 10;
const int inf1 = (int) 1e9 + 10;
#define int long long
#define dbl long double
#define endl '\n'
#define sc second
#define fr first
#define mp make_pair
#define pb push_back
#define all(x) x.begin(), x.end()
const int maxn = 1e5+10;

int n, in[maxn], out[maxn], dp[maxn], sub[maxn], sp[maxn];
int h[maxn], d[maxn], par[maxn], timer, s, q, rt, tr[4*maxn];
vector<pair<int,int>> g[maxn], edg, qrys[maxn];
pair<int,string> ansq[maxn];

void dfsdp(int u, int ant) {
    in[u] = ++timer;
    dp[u] = inf;
    sub[u] = 1;
    if(sp[u]) dp[u] = d[u];

    for(auto V : g[u]) if(V.fr != ant) {
        int v = V.fr;
        int w = V.sc;
        h[v] = h[u]+1;
        d[v] = d[u]+w;
        par[v] = u;
        dfsdp(v,u);
        sub[u]+= sub[v];
        dp[u] = min(dp[u],dp[v]);
    }

    out[u] = timer;
}

void build(int no, int l, int r) {
    tr[no] = inf;
    if(l == r) return;
    int lc=2*no,rc=2*no+1,mid=(l+r)>>1;
    build(lc,l,mid);
    build(rc,mid+1,r);
}

void upd(int no, int l, int r, int pos, int val) {
    if(l > pos || r < pos) return;
    if(l == r) {
        tr[no] = val;
        return;
    }
    int lc=2*no,rc=2*no+1,mid=(l+r)>>1;
    upd(lc,l,mid,pos,val);
    upd(rc,mid+1,r,pos,val);
    tr[no] = min(tr[lc],tr[rc]);
}

int qry(int no, int l, int r, int L, int R) {
    if(l > R || r < L) return inf;
    if(l >= L && r <= R) return tr[no];
    int lc=2*no,rc=2*no+1,mid=(l+r)>>1;
    return min(qry(lc,l,mid,L,R),qry(rc,mid+1,r,L,R));
}

void dfsqry(int u, int ant) {
    if(dp[u] == inf) upd(1,0,n,h[u],inf);
    else upd(1,0,n,h[u],dp[u]-2*d[u]);

    for(auto X : qrys[u]) {
        int id = X.fr;
        int i = X.sc;
        int b;
        if(h[edg[id-1].fr] > h[edg[id-1].sc]) b = edg[id-1].fr;
        else b = edg[id-1].sc;

        if(in[b] <= in[u] && in[u] <= out[b]) {
            int ans = qry(1,0,n,h[b],h[u]);

            if(ans == inf) ansq[i] = mp(-1,"oo");
            else ansq[i] = mp(ans+d[u],"");
        }
        else {
            ansq[i] = mp(-1,"escaped");
        }
    }

    for(auto V : g[u]) if(V.fr != ant) {
        int v = V.fr;
        dfsqry(v,u);
    }

}

void solve() {
    cin >> n >> s >> q >> rt;

    for(int i = 1; i <= n-1; i++) {
        int u,v,w; cin >> u >> v >> w;
        g[u].pb(mp(v,w));
        g[v].pb(mp(u,w));
        edg.pb(mp(u,v));
    }
    for(int i = 1; i <= s; i++) {
        int v; cin >> v;
        sp[v] = 1;
    }
    dfsdp(rt,0);

    for(int i = 1; i <= q; i++) {
        int id, u; cin >> id >> u;
        qrys[u].pb(mp(id,i));
    }

    build(1,0,n);
    dfsqry(rt,0);

    for(int i = 1; i <= q; i++) {
        if(ansq[i].fr == -1) cout << ansq[i].sc << endl;
        else cout << ansq[i].fr << endl;
    }

    // while(q--) {
    //     int id, u;
    //     cin >> id >> u;

    //     int b;
    //     if(h[edg[id-1].fr] > h[edg[id-1].sc]) b = edg[id-1].fr;
    //     else b = edg[id-1].sc;

    //     if(in[b] <= in[u] && in[u] <= out[b]) {
    //         int ans = inf;
    //         int v = u;
    //         while(true) {
    //             if(dp[v] != inf) {
    //                 ans = min(ans, dp[v]-2*d[v]);
    //             }
    //             if(v == b) break;
    //             v = par[v];
    //         }

    //         if(ans == inf) cout << "oo" << endl;
    //         else cout << ans+d[u] << endl;
    //     }
    //     else {
    //         cout << "escaped" << endl;
    //     }
    // }

}

int32_t main() {
    ios::sync_with_stdio(false); cin.tie(0);

    // freopen("in.in", "r", stdin);
    // freopen("out.out", "w", stdout);
    int tt = 1;
    // cin >> tt;
    while(tt--) {
        solve();
    }

}

• Subtask 1: 9 / 9
• Subtask 2: 27 / 27
• Subtask 3: 23 / 23
• Subtask 4: 41 / 41