Submission #564128

#	Time	Username	Problem	Language	Result	Execution time	Memory
564128		tamthegod	Race (IOI11_race)	C++14	9 / 100	289 ms	43304 KiB

race

#include<iostream>
#include<iomanip>
#include<algorithm>
#include<stack>
#include<queue>
#include<string>
#include<string.h>
#include<cmath>
#include<vector>
#include<map>
#include<unordered_map>
#include<set>
#include<unordered_set>
#include<cstdio>
#include<bitset>
#include<chrono>
#include<random>
#include<ext/rope>
/* ordered_set
#include<ext/pb_ds/assoc_container.hpp>
#include<ext/pb_ds/tree_policy.hpp>
using namespace __gnu_pbds;
#define ordered_set tree<int, null_type,less<int>, rb_tree_tag,tree_order_statistics_node_update>
*/
#define pb push_back
#define fi first
#define se second
using namespace std;
using ll = long long;
using ld = long double;
using ull = unsigned long long;
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
const int maxN = 1e6 + 5;
const int mod = 1e9 + 7;
const ll oo = 1e18;
int n, k;
vector<pair<int, int>> adj[maxN];
int depth[maxN], lg[maxN];
int f[maxN][21];
ll dp[maxN];
void Log()
{
    for(int i=2; i<maxN; i++) lg[i] = lg[i / 2] + 1;
}
void predfs(int u, int par)
{
    for(pair<int, int> a : adj[u])
    {
        int v = a.fi, w = a.se;
        if(v == par) continue;
        dp[v] = dp[u] + w;
        depth[v] = depth[u] + 1;
        f[v][0] = u;
        for(int i=1; i<=lg[n]; i++)
            f[v][i] = f[f[v][i - 1]][i - 1];
        predfs(v, u);
    }
}
int lca(int u, int v)
{
    if(depth[u] < depth[v]) swap(u, v);
    int k = depth[u] - depth[v];
    for(int i=lg[n]; i>=0; i--)
    {
        if(k & (1 << i))
        {
            u = f[u][i];
            k -= (1 << i);
        }
    }
    if(u == v) return u;
    for(int i=lg[n]; i>=0; i--)
    {
        if(f[u][i] != f[v][i])
        {
            u = f[u][i];
            v = f[v][i];
        }
    }
    return f[u][0];
}
int Kth_Ancestor(int u, int k)
{
    for(int i=lg[n]; i>=0; i--)
    {
        if(k & (1 << i))
        {
            u = f[u][i];
            k -= (1 << i);
        }
    }
    return u;
}
ll dist(int u, int v)
{
    return dp[u] + dp[v] - 2 * dp[lca(u, v)];
}
ll res = oo;
void dfs(int u, int par)
{
    for(pair<int, int> a : adj[u])
    {
        int v = a.fi, w = a.se;
        if(v == par) continue;
        dfs(v, u);
    }
    ll low = 1, high = depth[u], mid;
    while(low <= high)
    {
        mid = (low + high) / 2;
        int p = Kth_Ancestor(u, mid);
        if(dist(u, p) >= k) high = mid - 1;
        else low = mid + 1;
    }
    int p = Kth_Ancestor(u, low);
    if(dist(u, p) == k) res = min(res, low);
}
int best_path(int N, int K, int H[][2], int L[2])
{
    n = N;
    k = K;
    for(int i=0; i<n; i++)
    {
        H[i][0]++;
        H[i][1]++;
        adj[H[i][0]].pb({H[i][1], L[i]});
        adj[H[i][1]].pb({H[i][0], L[i]});
    }
    Log();
    predfs(1, 0);
    dfs(1, 0);
    return res < oo ? res : -1;
}

Compilation message (stderr)

race.cpp: In function 'void dfs(int, int)':
race.cpp:103:23: warning: unused variable 'w' [-Wunused-variable]
  103 |         int v = a.fi, w = a.se;
      |                       ^

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