Submission #764703

#	Time	Username	Problem	Language	Result	Execution time	Memory
764703		Magikarp4000	Race (IOI11_race)	C++17	0 / 100	5 ms	9684 KiB

race

#include "race.h"
#include <bits/stdc++.h>
using namespace std;
#define OPTM ios_base::sync_with_stdio(0); cin.tie(0);
#define INF int(1e9+7)
#define ln '\n' 
#define ll long long
#define ull unsigned long long
#define ui unsigned int
#define us unsigned short
#define FOR(i,s,n) for (int i = s; i < n; i++)
#define FORR(i,n,s) for (int i = n; i > s; i--)
#define FORX(u, arr) for (auto u : arr)
#define PB push_back
#define in(v,x) (v.find(x) != v.end())
#define F first
#define S second
#define PII pair<int, int>
#define PLL pair<ll, ll>
#define UM unordered_map
#define US unordered_set
#define PQ priority_queue
#define ALL(v) v.begin(), v.end()
const ll LLINF = 1e18+1;
#define int long long

struct Edge {
    int F,w;
};

const int MAXN = 2e5+1, LOG = 19;
int n,k;
set<PII> v[MAXN];
int dist[MAXN], len[MAXN], p[MAXN], sz[MAXN];
UM<int,PII> mp;
int jump[MAXN][LOG];
int res = LLINF;

void pre_dfs(int s, int pa) {
    FORX(u,v[s]) {
        if (u.F == pa) continue;
        dist[u.F] = dist[s]+1;
        len[u.F] = len[s]+u.S;
        p[u.F] = s;
        pre_dfs(u.F,s);
    }
}

void pre_lca() {
    FOR(i,0,n) jump[i][0] = p[i];
    FOR(j,1,LOG) {
        FOR(i,0,n) {
            jump[i][j] = jump[jump[i][j-1]][j-1];
        }
    }
}

int lca(int a, int b) {
    if (dist[a] < dist[b]) swap(a,b);
    FORR(j,LOG-1,-1) {
        if (dist[a]-(1<<j) >= dist[b]) a = jump[a][j];
    }
    if (a == b) return a;
    FORR(j,LOG-1,-1) {
        if (jump[a][j] != jump[b][j]) {
            a = jump[a][j];
            b = jump[b][j];
        }
    }
    return p[a];
}

int find_centroid(int s, int pa, int num) {
    FORX(u,v[s]) {
        if (u.F == pa) continue;
        if (sz[u.F] > num/2) return find_centroid(u.F,s,num);
    }
    return s;
}

void dfs(int s, int pa) {
    sz[s] = 1;
    FORX(u,v[s]) {
        if (u.F == pa) continue;
        dfs(u.F,s);
        sz[s] += sz[u.F];
    }
}

void dfs1(int s, int pa, int src) {
    FORX(u,v[s]) {
        if (u.F == pa) continue;
        int anc = lca(u.F,src);
        int l = len[u.F]+len[src]-2*len[anc];
        int d = dist[u.F]+dist[src]-2*dist[anc];
        if (!mp.count(l)) {
            mp[l].F = d;
            mp[l].S = LLINF;
        }
        else if (d < mp[l].F) {
            mp[l].S = mp[l].F;
            mp[l].F = d;
        }
        else if (d < mp[l].S) mp[l].S = d;
        dfs1(u.F,s,src);
    }
}

void decomp(int s, int pa) {
    mp.clear();
    dfs(s,pa);
    int c = find_centroid(s,pa,sz[s]);
    dfs1(c,-1,c);
    FORX(u,mp) {
        if (u.F == k) res = min(res, u.S.F);
        else if (u.F < k) {
            if (2*u.F == k) res = min(res, u.S.F+u.S.S);
            else if (mp.count(k-u.F)) res = min(res, u.S.F+mp[k-u.F].F);
        }
    }
    vector<PII> tmp;
    FORX(u,v[s]) if (u.F != pa) tmp.PB(u);
    FORX(u,tmp) {
        v[s].erase(u);
        v[u.F].erase({s,u.S});
        decomp(u.F,c);
    }
}

int32_t best_path(int32_t N, int32_t K, int32_t H[][2], int32_t L[]) {
    n = N; k = K;
    FOR(i,0,n-1) {
        v[H[i][0]].insert({H[i][1],L[i]});
        v[H[i][1]].insert({H[i][0],L[i]});
    }
    pre_dfs(0,-1);
    pre_lca();
    decomp(0,-1);
    return res == LLINF ? -1 : res;
}

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