Submission #638939

#	Time	Username	Problem	Language	Result	Execution time	Memory
638939		BackNoob	Race (IOI11_race)	C++14	0 / 100	3 ms	4948 KiB

race

#include <bits/stdc++.h>
#include "race.h"
#define ll long long
#define fi first
#define se second
#define endl '\n'
#define MASK(i) (1LL << (i))
#define ull unsigned long long
#define ld long double
#define pb push_back
#define all(x) (x).begin() , (x).end()
#define BIT(x , i) ((x >> (i)) & 1)
#define TASK "task"
#define sz(s) (int) (s).size()

using namespace std;
const int mxN = 2e5 + 227;
const int inf = 1e9 + 277;
const int mod = 1e9 + 7;
const ll infll = 1e18 + 7;
const int base = 307;
const int LOG = 20;

template <typename T1, typename T2> bool minimize(T1 &a, T2 b) {
	if (a > b) {a = b; return true;} return false;
}
template <typename T1, typename T2> bool maximize(T1 &a, T2 b) {
	if (a < b) {a = b; return true;} return false;
}

int n;
int k;
int res = inf;
int h[mxN][2];
int l[mxN];
int sub[mxN];
int dist[mxN];
int parcen[mxN];
vector<int> node;
vector<pair<int, int>> adj[mxN];
ll rdist[mxN];
bool removed[mxN];
map<ll, int> mp;

void dfs(int u, int p)
{
    for(auto it : adj[u]) {
        int v = it.fi;
        int c = it.se;
        if(v == p) continue;
        dfs(v, u);
    }
}

void dfs_sz(int u, int p)
{
    sub[u] = 1;
    for(auto it : adj[u]) {
        int v = it.fi;
        int c = it.se;
        if(v == p || removed[v] == true) continue;
        dfs_sz(v, u);
        sub[u] += sub[v];
    }
}

int dfs_cen(int u, int p, int n)
{
    for(auto it : adj[u]) {
        int v = it.fi;
        int c = it.se;
        if(v == p || removed[v] == true) continue;
        if(sub[u] > n / 2) return dfs_cen(v, u, n);
    }
    return u;
}

void find_best(int u, int p, int root)
{
    node.pb(u);
    for(auto it : adj[u]) {
        int v = it.fi;
        int c = it.se;
        if(v == p) continue;
        rdist[v] = rdist[u] + c;
        dist[v] = dist[u] + 1;
        if(rdist[v] == k) minimize(res, dist[v]);
        if(k > rdist[v]) {
            if(mp.count(k - rdist[v]) != 0) {
                minimize(res, dist[v] + mp[k - rdist[v]]);
            }
        }
        if(u == root) {
            for(auto it : node) {
                if(mp.count(dist[it]) == 0) mp[dist[it]] = rdist[it];
                else minimize(mp[dist[it]], rdist[it]);
            }
            node.clear();
        }
        find_best(v, u, root);
    }
}

void init_centroid(int u, int p)
{
    parcen[u] = p;
    dfs_sz(u, -1);
    int c = dfs_cen(u, -1, sub[u]);
    removed[c] = true;

    node.clear();
    mp.clear();
    rdist[c] = 0;
    dist[c] = 0;
    find_best(c, -1, c);
    removed[c] = true;

    for(auto it : adj[c]) {
        int v = it.fi;
        if(removed[v] == false || v == p) init_centroid(v, u);
    }
}


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

    dfs(1, -1);
    //par[1][0] = 1;
    //for(int j = 1; j <= LOG; j++)
    //for(int i = 1; i <= n; i++) par[i][j] = par[par[i][j - 1]][j - 1];

    init_centroid(1, -1);
    if(res == inf) return -1;
    return res;
}

Compilation message (stderr)

race.cpp: In function 'void dfs(int, int)':
race.cpp:49:13: warning: unused variable 'c' [-Wunused-variable]
   49 |         int c = it.se;
      |             ^
race.cpp: In function 'void dfs_sz(int, int)':
race.cpp:60:13: warning: unused variable 'c' [-Wunused-variable]
   60 |         int c = it.se;
      |             ^
race.cpp: In function 'int dfs_cen(int, int, int)':
race.cpp:71:13: warning: unused variable 'c' [-Wunused-variable]
   71 |         int c = it.se;
      |             ^

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