Submission #1102489

#	Time	Username	Problem	Language	Result	Execution time	Memory
1102489		InvMOD	Valley (BOI19_valley)	C++14	100 / 100	95 ms	72268 KiB

valley

#include <bits/stdc++.h>
using namespace std;

#define fi first
#define se second
#define gcd __gcd
#define vsz(v) (int) v.size()
#define pb push_back
#define pi pair<int,int>
#define all(v) (v).begin(), (v).end()
#define compact(v) (v).erase(unique(all(v)), (v).end())
#define FOR(i, a, b) for(int i = (a); i <= (b); i++)
///#define int long long

using ll = long long;
using ld = long double;
using ull = unsigned long long;

template<typename T> bool ckmx(T& a, const T& b){if(a < b) return a = b, true; return false;}
template<typename T> bool ckmn(T& a, const T& b){if(a > b) return a = b, true; return false;}

const int N = 2e5+5;
const ll MOD = 1e9+7;
const ll INF = 1e18;
const int lg = 21;


int n, cntShop, Exit, q, timerDFS;
int tin[N], tout[N], par[lg][N], h[N];
ll near[N], val[lg][N], dist[N];
bool isShop[N];
pair<int,int> E[N];
vector<pair<int,int>> adj[N];

void dfs(int x, int p){
    tin[x] = ++timerDFS;
    near[x] = (isShop[x] ? 0 : INF);
    for(pair<int,int> e : adj[x])if(e.fi != p){
        int v = e.fi; ll w = e.se;

        h[v] = h[x] + 1;
        dist[v] = dist[x] + w;

        par[0][v] = x;
        for(int i = 1; i < lg; i++) par[i][v] = par[i-1][par[i-1][v]];
        dfs(v, x);

        ckmn(near[x], near[v] + w);
    }
    tout[x] = ++timerDFS;
    return;
}

ll get_val(int x, int asc){
    assert(h[x] >= h[asc]);
    int k = h[x] - h[asc] + 1; ll res = INF;
    for(int i = 0; i < lg; i++){
        if(k >> i & 1){
            ckmn(res, val[i][x]);
            x = par[i][x];
        }
    }
    return res;
}

bool in(int u, int v){
    return tin[u] <= tin[v] and tout[v] <= tout[u];
}

void solve()
{
    cin >> n >> cntShop >> q >> Exit;
    for(int i = 1; i < n; i++){
        int u,v,w; cin >> u >> v >> w;
        adj[u].pb(make_pair(v, w));
        adj[v].pb(make_pair(u, w));
        E[i] = make_pair(u, v);
    }

    for(int i = 1; i <= cntShop; i++){
        int v; cin >> v;
        isShop[v] = true;
    }

    dfs(Exit, -1);

    for(int i = 1; i <= n; i++){
        /// dist(u,v) = dist[u] + dist[v] - 2 * dist[lca(u,v)]
        /// near[i] = dist[v] - dist[lca(u,v)] so val[0][i] will be -dist[lca(u,v)] + near[i]
        if(near[i] != INF) val[0][i] = -1 * dist[i] + near[i];
        else{
            val[0][i] = INF;
        }
    }

    for(int i = 1; i < lg; i++){
        for(int j = 1; j <= n; j++){
            val[i][j] = min(val[i-1][j], val[i-1][par[i-1][j]]);
        }
    }

    for(int i = 1; i < n; i++){
        if(h[E[i].fi] > h[E[i].se]) swap(E[i].fi, E[i].se);
    }

    while(q--){
        int i,R; cin >> i >> R;
        int v = E[i].se;
        if(!in(v, R)){
            cout << "escaped\n";
        }
        else{
            ll answer = get_val(R, v);
            if(answer == INF){
                cout << "oo\n";
            }
            else cout << answer + dist[R] <<"\n";
        }
    }
    return;
}

signed main()
{
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);

    #define name "InvMOD"
    if(fopen(name".INP", "r")){
        freopen(name".INP","r",stdin);
        freopen(name".OUT","w",stdout);
    }

    int t = 1; //cin >> t;
    while(t--) solve();
    return 0;
}

Compilation message (stderr)

valley.cpp: In function 'int main()':
valley.cpp:131:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  131 |         freopen(name".INP","r",stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~
valley.cpp:132:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  132 |         freopen(name".OUT","w",stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~

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