Submission #1209813

#	Time	Username	Problem	Language	Result	Execution time	Memory
1209813		nvc2k8	Race (IOI11_race)	C++20	100 / 100	622 ms	38204 KiB

race

#include <bits/stdc++.h>
#include "race.h"
#define TASK "race"
#define INT_LIM (int) 2147483647
#define LL_LIM (long long) 9223372036854775807
#define endl '\n'
#define mp make_pair
#define pb push_back
#define fi first
#define se second
#define BIT(i,x) (((i)>>(x))&1)
#define FOR(i,a,b) for(int i = (a); i<=(b); i++)
#define FORD(i,a,b) for(int i = (a); i>=(b); i--)
#define ll long long
#define pii pair<int,int>
using namespace std;
///------------------------------------------///
int n,k, ans = INT_LIM;
vector<pii> adj[200005];
bool dis[200005];
int sz[200005];

void initsize(int u, int p)
{
    sz[u] = 1;
    for (auto V:adj[u]) if (V.fi!=p && !dis[V.fi])
    {
        initsize(V.fi, u);
        sz[u]+= sz[V.fi];
    }
}

int findcentroid(int u, int p, int n)
{
    for (auto V:adj[u]) if (V.fi!=p && !dis[V.fi] && sz[V.fi]>n/2)
    {
        return findcentroid(V.fi, u, n);
    }

    return u;
}

map<int,int> f;

void dfs(int u, int p, int deep, int d, bool upd)
{
    if (d>k) return;
    if (!upd)
    {
        if (f.find(k-d)!=f.end())
        {
            ans = min(ans, f[k-d]+deep);
        }
    }
    else
    {
        if (f.find(d)!=f.end()) f[d] = min(f[d], deep);
        else f[d] = deep;
    }

    for (auto V:adj[u]) if (V.fi!=p && !dis[V.fi])
    {
        int v = V.fi, w = V.se;
        dfs(v, u, deep+1, d+w, upd);
    }
}

void process(int u)
{
    f.clear();
    f[0] = 0;

    for (auto V:adj[u]) if (!dis[V.fi])
    {
        int v = V.fi, w = V.se;
        dfs(v, u, 1, w, 0);
        dfs(v, u, 1, w, 1);
    }
}

void decompose(int u)
{
    initsize(u, -1);
    u = findcentroid(u, -1, sz[u]);
    process(u);

    dis[u] = true;
    for (auto V:adj[u]) if (!dis[V.fi])
    {
        decompose(V.fi);
    }
}

int best_path(int N, int K, int h[][2], int l[])
{
    n = N; k = K;
    FOR(i, 0, n-2)
    {
        int u = h[i][0]+1, v = h[i][1]+1;
        adj[u].pb(mp(v,l[i]));
        adj[v].pb(mp(u,l[i]));
    }

    decompose(1);



    if (ans==INT_LIM) return -1;
    return ans;
}

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