Submission #1025982

#	Time	Username	Problem	Language	Result	Execution time	Memory
1025982		PVSekhar	Race (IOI11_race)	C++14	0 / 100	25 ms	48112 KiB

race

#include <bits/stdc++.h>
using namespace std; 
#define ll long long
// const ll MOD = 998244353;
const ll MOD = 1e9 + 7;
const ll NN = 2e5 + 2;
const ll KK = 1e6 + 2;

ll n, k, ans = NN;
vector<ll> is_dead(NN, 0), cnt(KK, -1), cnt1(KK, -1), sz(NN);
vector<vector<ll>> edges(NN);
map<pair<ll,ll>, ll> w;
set<ll> s, s1;

void comp_sz (ll node, ll parent) {
    sz[node] = 1;
    for (ll child : edges[node]) {
        if (child == parent || is_dead[child]) continue;
        comp_sz(child, node);
        sz[node] += sz[child];
    }
}

void dfs(ll node, ll parent, ll dist, ll lvl) {
    s1.insert(dist), cnt1[dist] = (cnt1[dist] == -1 ? lvl : min(cnt1[dist], lvl));
    for (ll child : edges[node]) {
        if (child == parent || is_dead[child]) continue;
        dfs(child, node, dist + w[make_pair(child, node)], lvl + 1);
    }
}

void find_cent (ll node, ll parent, ll size) {
    for (ll child : edges[node]) {
        if (child == parent || is_dead[child]) continue;
        if (sz[child] * 2 > size) {
            find_cent(child, node, size);
            return;
        }
    }
    s.insert(0);
    cnt[0] = 0;
    for (ll child : edges[node]) {
        if (is_dead[child]) continue;
        dfs(child, node, w[make_pair(child, node)], 1);
        for (ll x : s1) {
            if (s.find(k - x) != s.end()) ans = min(ans, cnt1[x] + cnt[k - x]);
        }
        for (ll x : s1) {
            s.insert(x);
            cnt[x] = (cnt[x] == -1 ? cnt1[x] : min(cnt1[x], cnt[x]));
            cnt1[x] = -1;
        }
        s1.clear();
    }
    for (ll x : s) {
        cnt[x] = -1;
    }
    s.clear();
    is_dead[node] = 1;
    for (ll child : edges[node]) {
        if (is_dead[child]) continue;
        comp_sz(child, node);
        find_cent(child, node, sz[child]);
    }
}

int best_path(int N, int K, int H[][2], int L[]){
    n = N, k = K;
    for (int i = 0; i < n - 1; i++) {
        H[i][0]++, H[i][1]++;
        edges[H[i][0]].push_back(H[i][1]);
        edges[H[i][1]].push_back(H[i][0]);
    }
    for (int i = 0; i < n - 1; i++) {
        w[make_pair(H[i][0], H[i][1])] = L[i];
        w[make_pair(H[i][1], H[i][0])] = L[i];
    }
    is_dead[0] = 1;
    comp_sz(1, 0);
    find_cent(1, 0, n);
    if (ans == NN) ans = -1;
    return ans;
}

• Subtask 1: 0 / 9
• Subtask 2: 0 / 12
• Subtask 3: 0 / 22
• Subtask 4: 0 / 57