Submission #1267870

#	Time	Username	Problem	Language	Result	Execution time	Memory
1267870		hoa208	Valley (BOI19_valley)	C++20	100 / 100	197 ms	46416 KiB

valley

#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define FOR(i, a, b) for (int i = (a), _b = (b); i <= _b; i++)
#define FORD(i, b, a) for (int i = (b), _a = (a); i >= _a; i--)
#define pa pair<ll, ll>
#define fi first
#define se second
#define bit(mask, j) ((mask >> j) & 1)
const   ll mod = 1e9 + 7;
const   ll INF = 1e18;
//--------------------------------------------------------------------

ll n, s, q, E;
const ll N = 1e5 + 10;
vector<pa> g[N];
ll dx[N];
ll dp[N], f[N], h[N], up[N][18], dist[N][18];
void dfs(ll u, ll p) {
    if(dx[u] == 1) dp[u] = f[u];
    else dp[u] = INF;
    for(auto e : g[u]) {
        ll v = e.fi, w = e.se;
        if(v == p) continue;
        h[v] = h[u] + 1;
        f[v] = f[u] + w;
        up[v][0] = u;
        FOR(i, 1, 17) {
            up[v][i] = up[up[v][i - 1]][i - 1];
        }
        dfs(v, u);
        dp[u] = min(dp[u], dp[v]);
    }
}
void build_dist() {
    FOR(u, 1, n) {
        if(up[u][0] == 0 || dp[up[u][0]] == INF) dist[u][0] = INF;
        else dist[u][0] = dp[up[u][0]] - 2 * f[up[u][0]];
    }
    FOR(i, 1, 17) {
        FOR(u, 1, n) {
            dist[u][i] = min(dist[up[u][i - 1]][i - 1], dist[u][i - 1]);
        }
    }
}
pa ed[N];
ll get(ll u, ll k) {
    for(int j = 0; (1 << j) <= k; j++) {
        if(bit(k, j)) u = up[u][j];
    }
    return u;
}
ll lca(ll u, ll v) {
    if(h[u] < h[v]) swap(u, v);
    u = get(u, h[u] - h[v]);
    if(u == v) return u;
    FORD(i, 17, 0) {
        if(up[v][i] == up[u][i]) {
            u = up[u][i];
            v = up[v][i];
        }
    }
    return up[u][0];
}
ll distance(ll u, ll v) {
    ll p = lca(u, v);
    return h[u] + h[v] - 2 * h[p];
}
void hbmt() {
    cin >> n >> s >> q >> E;
    FOR(i, 1, n - 1) {
        ll u, v, w;
        cin >> u >> v >> w;
        ed[i] = {u, v};
        g[u].push_back({v, w});
        g[v].push_back({u, w});
    }
    FOR(i, 1, s) {
        ll x;
        cin >> x;
        dx[x] = 1;
    }
    dfs(E, 0);
    build_dist();
    FOR(i, 1, q) {
        ll id, r;
        cin >> id >> r;
        ll u = ed[id].fi, v = ed[id].se;
        if(h[u] > h[v]) swap(u, v);
        if(distance(E, u) + distance(u, v) + distance(v, r) == distance(E, r)) {
            ll k = h[r] - h[v];
            ll mn = dp[r] == INF ? INF : dp[r] - 2 * f[r], cur = f[r];
            for(int j = 0; (1 << j) <= k; j++) {
                if(bit(k, j)) {
                    mn = min(dist[r][j], mn);
                    r = up[r][j];
                }
            }
            if(mn == INF) cout << "oo\n";
            else cout << mn + cur << '\n';
        }
        else {
            cout << "escaped\n";
        }
    }
}

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

    #define NAME "hbmt"
    if(fopen(NAME".inp", "r")) {
        freopen(NAME".inp", "r", stdin);
        freopen(NAME".out", "w", stdout);
    }
    
    //int t;cin>>t;while(t--)
    hbmt();
    return 0;
}

Compilation message (stderr)

valley.cpp: In function 'int main()':
valley.cpp:115:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  115 |         freopen(NAME".inp", "r", stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
valley.cpp:116:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  116 |         freopen(NAME".out", "w", stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~

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