Submission #639034

#	Time	Username	Problem	Language	Result	Execution time	Memory
639034		thienbao1602	Race (IOI11_race)	C++17	100 / 100	496 ms	103244 KiB

race

#include    <bits/stdc++.h>
#define ll long long
#define pi pair<ll, ll>
#define fi first
#define se second
#define sz(x) (int)(x.size())
using namespace std;

const int Nmax = 2e5 + 55;
const ll inf = 1e17;

int N, dist[Nmax];
ll sum[Nmax], K, bestWay = inf;
map<ll, ll> info[Nmax];
vector<pi> edges[Nmax];

void dfs(int u, int par, ll curSum, int deep)
{
    dist[u] = deep;
    sum[u] = curSum;
    info[u][curSum] = deep;

    for(auto [r, v] : edges[u])
    {
        if (v != par)
        {
            dfs(v, u, curSum + r, deep + 1);
        }
    }
}

void merge_small_to_large(int u, int par)
{
    ll target = K + 2 * sum[u];
    for(auto [r, v] : edges[u])
    {
        if (v != par)
        {
            merge_small_to_large(v, u);
            if (sz(info[u]) < sz(info[v])) swap(info[u], info[v]);
            for(auto x : info[v])
            {
                if (info[u].find(target - x.fi) != info[u].end())
                {
                    bestWay = min(bestWay, info[u][target - x.fi] + x.se  - 2 * dist[u]);
                }
            }

            for(auto x : info[v])
            {
                if (info[u].find(x.fi) == info[u].end())
                {
                    info[u][x.fi] = x.se;
                } else
                {
                    info[u][x.fi] = min(info[u][x.fi], x.se);
                }
            }
        }
    }
}

int best_path(int n, int k, int H[][2], int L[])
{
    N = n, K = k;
    for(int i=0; i<n-1; i++)
    {
        edges[H[i][0]].push_back({L[i], H[i][1]});
        edges[H[i][1]].push_back({L[i], H[i][0]});
    }

    dfs(0, n + 1, 0, 0);
    merge_small_to_large(0, n + 1);
    return (bestWay == inf ? -1 : bestWay);
}

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