Submission #1027441

#	Time	Username	Problem	Language	Result	Execution time	Memory
1027441		onbert	Race (IOI11_race)	C++17	100 / 100	1557 ms	225768 KiB

race

#include "race.h"
#include <bits/stdc++.h>
using namespace std;
#define int long long
struct thing {
    int dist, d, u;
    bool operator < (const thing &b) const {
        if (dist!=b.dist) return dist < b.dist;
        if (d!=b.d) return d < b.d;
        return u < b.u;
    }
};
struct node {
    pair<int,int> val;
    int lpt, rpt;
};

const int maxn = 2e5 + 5, maxN = 8e5 + 5, INF = 1e18;
int n, k;
vector<pair<int,int>> adj[maxn];
int sz[maxn], dist[maxn], d[maxn];
bool cmp(pair<int,int> x, pair<int,int> y) {
    return sz[x.first] > sz[y.first];
}

void dfs0(int u) {
    sz[u] = 1;
    for (auto [v, w]:adj[u]) {
        adj[v].erase(find(adj[v].begin(), adj[v].end(), make_pair(u, w)));
        dist[v] = dist[u] + w, d[v] = d[u] + 1;
        dfs0(v);
        sz[u] += sz[v];
    }
    sort(adj[u].begin(), adj[u].end(), cmp);
}
int newid[maxn], oldid[maxn], lim[maxn], cnt = -1;
void dfs1(int u) {
    cnt++;
    newid[u] = cnt, oldid[cnt] = u;
    for (auto [v, w]:adj[u]) dfs1(v);
    lim[u] = cnt;
}

vector<node> seg[maxN];
void build(int id, int l, int r) {
    seg[id] = {{{-INF, -INF}, 0, 0}};
    if (l==r) return;
    int mid = (l+r)/2;
    build(id*2, l, mid); build(id*2+1, mid+1, r);
}
void update(int id, int l, int r, int target, pair<int,int> val) {
    if (r<target || target<l) return;
    if (l==r) {
        seg[id].push_back({val, 0, 0});
        return;
    }
    int mid = (l+r)/2;
    update(id*2, l, mid, target, val); update(id*2+1, mid+1, r, target, val);
    pair<int,int> cur = max(seg[id*2].back().val, seg[id*2+1].back().val);
    seg[id].push_back({cur, (int)seg[id*2].size()-1, (int)seg[id*2+1].size()-1});
}
pair<int,int> qry(int id, int pt, int l, int r, int findl, int findr) {
    if (r<findl || findr<l) return {-INF, -INF};
    if (findl<=l && r<=findr) return seg[id][pt].val;
    int mid = (l+r)/2;
    pair<int,int> lhs = qry(id*2, seg[id][pt].lpt, l, mid, findl, findr);
    pair<int,int> rhs = qry(id*2+1, seg[id][pt].rpt, mid+1, r, findl, findr);
    return max(lhs, rhs);
}

int ans = INF, curD;
vector<thing> vec = {{-INF, -INF, -INF}};
void QRY(int l, int r, int val) {
    if (val<0) return;
    thing cur = {val, INF, INF};
    int pos = upper_bound(vec.begin(), vec.end(), cur) - vec.begin() - 1;
    // cout << l << " " << r << " " << val << " " << pos << endl;
    pair<int,int> temp = qry(1, pos, 0, n-1, l, r);
    // cout << temp.first << " " << temp.second << endl;
    if (temp.first!=val) return;
    ans = min(-temp.second + curD, ans);
}

int32_t best_path(int32_t N, int32_t K, int32_t H[][2], int32_t L[]) {
    n = N, k = K;
    for (int i=0;i<n-1;i++) {
        auto [u, v] = H[i];
        adj[u].push_back({v, L[i]});
        adj[v].push_back({u, L[i]});
    }
    dist[0] = 0, d[0] = 0;
    dfs0(0); dfs1(0);
    // for (int i=0;i<n;i++) cout << newid[i] << " "; cout << endl;
    for (int i=0;i<n;i++) vec.push_back({dist[i], -d[i], newid[i]});
    sort(vec.begin(), vec.end());
    build(1, 0, n-1);
    for (int i=1;i<=n;i++) {
        update(1, 0, n-1, vec[i].u, {vec[i].dist, vec[i].d});
        // cout << i << " " << vec[i].u << " " << vec[i].dist << " " << vec[i].d << endl;
    }
    for (int u=0;u<n;u++) {
        curD = -d[u];
        // if (u==6) cout << "TEST" << endl;
        QRY(newid[u]+1, lim[u], k + dist[u]);
        // if (u==6) cout << k+dist[u] << endl;
        for (int i=1;i<adj[u].size();i++) {
            int v = adj[u][i].first;
            for (int j=newid[v];j<=lim[v];j++) {
                curD = -2*d[u] + d[oldid[j]];
                QRY(newid[u]+1, newid[v]-1, k + 2*dist[u] - dist[oldid[j]]);
            }
        }
    }
    if (ans==INF) return -1;
    return ans;
}

Compilation message (stderr)

race.cpp: In function 'int32_t best_path(int32_t, int32_t, int32_t (*)[2], int32_t*)':
race.cpp:106:23: warning: comparison of integer expressions of different signedness: 'long long int' and 'std::vector<std::pair<long long int, long long int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
  106 |         for (int i=1;i<adj[u].size();i++) {
      |                      ~^~~~~~~~~~~~~~

• Subtask 1: 9 / 9
• Subtask 2: 12 / 12
• Subtask 3: 22 / 22
• Subtask 4: 57 / 57