Submission #1287498

#	Time	Username	Problem	Language	Result	Execution time	Memory
1287498		Ice_man	Race (IOI11_race)	C++17	0 / 100	6 ms	12088 KiB

race

/**
 ____    ____    ____    __________________    ____    ____    ____
||I ||  ||c ||  ||e ||  ||                ||  ||M ||  ||a ||  ||n ||
||__||  ||__||  ||__||  ||________________||  ||__||  ||__||  ||__||
|/__\|  |/__\|  |/__\|  |/________________\|  |/__\|  |/__\|  |/__\|

*/

#include <iostream>
#include <vector>
#include <map>

#include "race.h"

#define maxn 500005
#define PB push_back
#define X first
#define Y second

typedef long long ll;
typedef std::pair<ll,ll> pll;

const ll INF = 4e18;

std::vector<pll> v[maxn];
int n, k;
ll ans;

ll sumv[maxn], distv[maxn];

struct dsu
{
    struct component
    {
        int par, sz;
        std::map<ll,ll> store;

        void init(int x)
        {
            par = x;
            sz = 1;
            store.clear();
        }

        void _swap(component& other)
        {
            std::swap(sz, other.sz);
            store.swap(other.store);
        }

        void insert(ll key, ll val)
        {
            auto it = store.find(key);
            if(it == store.end()) store.emplace(key, val);
            else it->second = std::min(it->second, val);
        }

        ll get(ll key)
        {
            auto it = store.find(key);
            if(it != store.end()) return it->second;
            return INF;
        }

        void _merge(component& other, ll target, int depth_u)
        {
            for(auto &e : other.store)
            {
                ll keyB = e.X;
                ll valB = e.Y;
                ll need = target - keyB;
                auto it = store.find(need);
                if(it != store.end())
                {
                    ll cand = it->second + valB - 2LL * depth_u;
                    if(cand < ans) ans = cand;
                }
            }

            for(auto &e : other.store)
            {
                auto it = store.find(e.X);
                if(it == store.end()) store.insert(e);
                else it->second = std::min(it->second, e.Y);
            }

            sz += other.sz;
        }
    };

    std::vector<component> un;

    void init(int sz)
    {
        un.resize(sz + 1);
        for(int i = 1; i <= n; i++)
            un[i].init(i);
    }

    int find_par(int node)
    {
        return node == un[node].par ? node : un[node].par = find_par(un[node].par);
    }

    void unite(int u, int v, int depth_u)
    {
        u = find_par(u);
        v = find_par(v);
        if(u == v) return;

        component &A = un[u];
        component &B = un[v];

        ll target = k + 2LL * sumv[u];

        if(A.sz < B.sz)
        {
            std::swap(A, B);
            std::swap(u, v);
        }

        A._merge(B, target, depth_u);

        B.par = u;
        B.store.clear();
    }
};

dsu uni;

void precomp(int u, int p, ll acc, int depth)
{
    sumv[u] = acc;
    distv[u] = depth;
    uni.un[u].store[acc] = depth;

    for(auto &nb : v[u])
    {
        if(nb.X == p) continue;
        precomp(nb.X, u, acc + nb.Y, depth + 1);
    }
}

void dfs(int node, int par)
{
    for(auto &nb : v[node])
    {
        if(nb.X == par) continue;

        dfs(nb.X, node);
        uni.unite(node, nb.X, distv[node]);
    }
}

int best_path(int N, int K, int h[][2], int L[])
{
    n = N;
    k = K;
    ans = INF;

    for(int i = 1; i <= n; i++)
    {
        v[i].clear();
    }

    for(int i = 0; i < n - 1; i++)
    {
        int a = h[i][0] + 1;
        int b = h[i][1] + 1;
        ll w = L[i];
        v[a].PB({b, w});
        v[b].PB({a, w});
    }

    uni.init(n + 5);
    precomp(1, 0, 0, 0);
    dfs(1, 0);

    if(ans == INF) return -1;
    return (int)ans;
}

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