Submission #555730

#	Time	Username	Problem	Language	Result	Execution time	Memory
555730		SavicS	Valley (BOI19_valley)	C++17	100 / 100	215 ms	44028 KiB

valley

#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
#include <bits/stdc++.h>
 
using namespace std;
using namespace __gnu_pbds;
 
typedef long long ll;
typedef long double ld;
 
typedef pair<int,int> pii;
typedef pair<ll,ll> pll;
typedef pair<ld,ld> pdd;
 
#define ff(i,a,b) for(int i = a; i <= b; i++)
#define fb(i,b,a) for(int i = b; i >= a; i--)
#define trav(a,x) for (auto& a : x)
 
#define sz(a) (int)(a).size()
#define pb push_back
#define fi first
#define se second
#define lb lower_bound
#define ub upper_bound
#define all(a) a.begin(), a.end()
#define rall(a) a.rbegin(), a.rend()
 
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());

template<typename T>
using ordered_set = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;

// os.order_of_key(k) the number of elements in the os less than k
// *os.find_by_order(k)  print the k-th smallest number in os(0-based)

const int mod = 1000000007;
const ll inf = 1e18 + 5;
const int mxN = 200005; 

int n, m, q, root;
pii edge[mxN];

vector<pii> g[mxN];
bool mark[mxN];

int timer = 0;
int in[mxN];
int out[mxN];
ll dist[mxN];
ll best[mxN];
int deda[mxN][20];
void dfs1(int v, int p){
    if(mark[v] == 1)best[v] = 0;
    
    deda[v][0] = p; 
    ff(i,1,19)deda[v][i] = deda[deda[v][i - 1]][i - 1];

    in[v] = ++timer;
    for(auto c : g[v]){
        int u = c.fi;
        int w = c.se;
        if(u != p){
            dist[u] = dist[v] + w; 
            dfs1(u, v);
            best[v] = min(best[v], best[u] + w);
        }
    }

    out[v] = timer;

}

ll mn[mxN][20];
void dfs2(int v, int p){
    if(p != 0 && best[p] != inf)mn[v][0] = best[p] - dist[p];
    ff(i,1,19)mn[v][i] = min(mn[v][i - 1], mn[deda[v][i - 1]][i - 1]);

    for(auto c : g[v]){
        if(c.fi != p){
            dfs2(c.fi, v);
        }
    }

}

// da li je y predak od x
bool predak(int x, int y){ return in[y] <= in[x] && in[x] <= out[y]; }

int main() {
    cin.tie(0)->sync_with_stdio(0);

    cin >> n >> m >> q >> root;
    ff(i,1,n - 1){
        int u, v, w;
        cin >> u >> v >> w;
        g[u].pb({v, w});
        g[v].pb({u, w});
        edge[i] = {u, v};
    }

    ff(i,1,m){
        int X;
        cin >> X;
        mark[X] = 1;
    }

    ff(i,1,n)best[i] = inf;
    ff(i,0,n)ff(j,0,19)mn[i][j] = inf;

    dfs1(root, 0); dfs2(root, 0);

    while(q--){
        int i, v;
        cin >> i >> v;

        int a = edge[i].fi;
        int b = edge[i].se;

        if(dist[a] < dist[b])swap(a, b);

        if(!predak(v, a)){
            cout << "escaped" << '\n';
            continue;
        }

        ll ans = (best[v] != inf ? best[v] - dist[v] : inf); int X = v;
        fb(j,19,0){
            if(deda[X][j] && dist[deda[X][j]] >= dist[a]){
                ans = min(ans, mn[X][j]);
                X = deda[X][j];
            }
        }

        if(ans == inf)cout << "oo" << '\n';
        else cout << ans + dist[v] << '\n';

    }

    return 0;
}
/*
 
5 2 3 1
1 2 3
1 3 2
3 4 1
3 5 2
2
4
2 2
2 5
4 5 

10 2 5 4
7 2 3
4 8 3
9 10 1
6 7 3
9 2 3
10 1 2
8 2 2
5 2 1
3 8 2
8
7
2 1
1 5
8 4
6 2
7 7
 
// probati bojenje sahovski
*/
 
 
 
 
 

• Subtask 1: 9 / 9
• Subtask 2: 27 / 27
• Subtask 3: 23 / 23
• Subtask 4: 41 / 41