Submission #1277423

#	Time	Username	Problem	Language	Result	Execution time	Memory
1277423		nhmktu	Race (IOI11_race)	C++17	0 / 100	2 ms	3128 KiB

race

#include <bits/stdc++.h>
#define ll long long
#define FOR(i,a,b) for(int i=a;i<=b;i++)
#define ROF(i,a,b) for(int i=a;i>=b;i--)
#define pi pair<int,int>
#define pii pair<int,pi>
#define fi first
#define se second
#define pb push_back
#define all(x) x.begin(), x.end()
#define sz(a) (int) a.size()
#define endl '\n'
#define data "data"

using namespace std;
const ll linf = 1e18;
const int inf = 1e9;
const int MOD = 1e9 + 7, M = 1e5;
const int MX = 1e6;

void add(int &a, int b)
{
    a += b;
    if(a>=MOD)
        a-=MOD;
    if(a<0)
        a += MOD;
}

int modulo(int x)
{
    if(x<=1)
        return 1;
    return (MOD - MOD/x) * modulo(MOD/x) % MOD;
}

int mul(int a, int b)
{
    return (1ll *a%MOD * b%MOD) % MOD;
}

int ans = inf;
int n, k;
int mn[MX+3];
int Sz[M+3];
bool iscent[M+3];
vector<pi> adj[M+3];

int dfs(int u, int p)
{
    Sz[u] = 1;
    FOR(i, 0, sz(adj[u]) -1)
    {
        int v = adj[u][i].fi;
        if(v == p || iscent[v]) continue;
        dfs(v, u);
        Sz[u] += Sz[v];
    }
}

int find_cent(int u, int tree_sz, int p)
{
    FOR(i, 0, sz(adj[u]) -1)
    {
        int v = adj[u][i].fi;
        if(v == p || iscent[v] || Sz[v] * 2 < tree_sz)
            return find_cent(v, tree_sz, u);
    }
    return u;
}

void compute(int u, int dept, bool f, int sum, int p)
{
    if(f == 1)
    {
        ans = max(ans, mn[k - sum] + dept);
    }
    else
    {
        mn[sum] = min(mn[sum], dept);
    }

    FOR(i, 0, sz(adj[u]) -1)
    {
        int v = adj[u][i].fi, w = adj[u][i].se;
        if(iscent[v] || v == p) continue;
        compute(v, dept + 1, f, sum + w, u);
    }
}

void Erase(int u, int dept, int sum, int p)
{
    mn[sum] = inf;
    FOR(i, 0, sz(adj[u]) -1)
    {
        int v = adj[u][i].fi, w = adj[u][i].se;
        if(iscent[v] || v == p) continue;
        Erase(v, dept + 1, sum + w, u);
    }
}

void build_cent(int u)
{
    dfs(u, -1);
    int cur = find_cent(u, Sz[u], u);
    iscent[cur] = 1;

    FOR(i, 0, sz(adj[cur]) -1)
    {
        int v = adj[cur][i].fi, w = adj[cur][i].se;
        if(iscent[v]) continue;
        compute(v, 1, 1, w, cur);
        compute(v, 1, 0, w, cur);
    }

    FOR(i, 0, sz(adj[cur]) -1)
    {
        int v = adj[cur][i].fi, w = adj[cur][i].se;
        if(iscent[v]) continue;
        Erase(v, 1, w, u);
    }

    FOR(i, 0, sz(adj[cur]) -1)
    {
        int v = adj[cur][i].fi;
        if(iscent[v]) continue;
        build_cent(v);
    }
}

void solve(void)
{
    FOR(i, 0, M) mn[i] = inf;
    build_cent(1);
}

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][1] + 1;
        int v = h[i][1] + 1;
        adj[u].pb({v, L[i]});
        adj[v].pb({u, L[i]});
    }

    solve();
    cout << ans;
}

Compilation message (stderr)

race.cpp: In function 'int dfs(int, int)':
race.cpp:59:1: warning: no return statement in function returning non-void [-Wreturn-type]
   59 | }
      | ^
race.cpp: In function 'int best_path(int, int, int (*)[2], int*)':
race.cpp:152:1: warning: no return statement in function returning non-void [-Wreturn-type]
  152 | }
      | ^

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