Submission #1117297

#	Time	Username	Problem	Language	Result	Execution time	Memory
1117297		gdragon	Valley (BOI19_valley)	C++17	100 / 100	402 ms	29520 KiB

valley

#include <bits/stdc++.h>
using namespace std;
#define TASK "long"
#define fi first
#define se second
#define ll long long
#define pb push_back
#define ALL(x) (x).begin(), (x).end()
#define GETBIT(mask, i) ((mask) >> (i) & 1)
#define MASK(i) ((1LL) << (i))
#define SZ(x) ((int)(x).size())
#define mp make_pair
#define CNTBIT(mask) __builtin_popcount(mask)
template<class X, class Y> bool maximize(X &x, Y y){ if (x < y) {x = y; return true;} return false;};
template<class X, class Y> bool minimize(X &x, Y y){ if (x > y) {x = y; return true;} return false;};
typedef pair<int, int> ii;
const int N = 1e5 + 5;
const long long INF = (long long)1e18 + 7;
const int mod = 1e9 + 7;
struct Fenwick {
    int n;
    vector<long long> v;
    Fenwick(int _n = 0) {
        n = _n;
        v.assign(n + 2, 0);
    }
    void update(int x, int c) {
        for(; x <= n; x += x & -x) v[x] += c;
    }
    long long get(int x) {
        long long ans = 0;
        for(; x > 0; x -= x & -x) ans += v[x];
        return ans;
    }
    long long get(int l, int r) {
        return (get(r) - get(l - 1));
    }
} fw;
struct SegTree {
    int n;
    vector<long long> st, lz;
    SegTree(int _n = 0) {
        n = _n;
        st.assign(4 * n + 5, INF);
        lz.assign(4 * n + 5, 0);
    }
    void down(int id) {
        long long &t = lz[id];
        if (t == 0) return;
        for(int i = (id<<1); i <= (id<<1|1); i++) {
            st[i] += (st[i] == INF ? 0 : t);
            lz[i] += t;
        }
        t = 0;
    }
    void update(int id, int l, int r, int u, int v, int c) {
        if (u > r || v < l) return;
        if (u <= l && r <= v) {
            // if (c == 2) cerr << "L R : " << l << ' ' << r << endl;
            st[id] += (st[id] == INF ? 0 : c);
            lz[id] += c;
            return;
        }
        down(id);
        int mid = (l + r) >> 1;
        update(id<<1, l, mid, u, v, c);
        update(id<<1|1, mid + 1, r, u, v, c);
        st[id] = min(st[id<<1], st[id<<1|1]);
    }
    void update(int l, int r, int c) {
        // if (c == 2) cout << l << ' ' << r << endl;
        if (c >= INF) return;
        return update(1, 1, n, l, r, c);
    }
    void update1(int id, int l, int r, int p, long long c) {
        if (l == r) {
            st[id] = c;
            return;
        }
        down(id);
        int mid = (l + r) >> 1;
        if (p <= mid) update1(id<<1, l, mid, p, c);
        else update1(id<<1|1, mid + 1, r, p, c);
        st[id] = min(st[id<<1], st[id<<1|1]);
    }
    void update1(int p, long long c) {
        if (c >= INF) return;
        return update1(1, 1, n, p, c);
    }
    long long get(int id, int l, int r, int u, int v) {
        if (u > r || v < l) return INF;
        if (u <= l && r <= v) return st[id];
        down(id);
        int mid = (l + r) >> 1;
        return min(get(id<<1, l, mid, u, v), get(id<<1|1, mid + 1, r, u, v)); 
    }
    long long get(int l, int r) {
        return get(1, 1, n, l, r);
    }
} it;
int n, q, numShop, root;
int tin[N], tout[N], high[N], head[N], sz[N], par[N];
bool isShop[N];
pair<long long, int> f1[N], f2[N];
pair<int, int> e[N];
vector<pair<int, int>> adj[N], queries[N];
vector<int> shops;
long long ans[N];
void read() {
    cin >> n >> numShop >> q >> root;
    for(int i = 1; i < n; i++) {
        int u, v, c; cin >> u >> v >> c;
        adj[u].push_back({v, c});
        adj[v].push_back({u, c});
        e[i] = {u, v};
    }
    shops.resize(numShop);
    for(auto&i : shops) {
        cin >> i;
        isShop[i] = 1;
    }
}
int timer = 0;
void dfs(int u, int p) {
    sz[u] = 1;
    par[u] = p;
    for(auto& i: adj[u]) {
        int v = i.fi;
        if (v == p) continue;
        high[v] = high[u] + 1;
        dfs(v, u);
        sz[u] += sz[v];
    }
}
bool isChild(int u, int p) {
    return tin[u] >= tin[p] && tin[u] <= tout[p];
}
void hld(int u, int p, int top, int w) {
    tin[u] = ++timer;
    head[u] = top;
    // cerr << u << ' ' << head[u] << endl;
    // if (p != -1) weight.update(tin[u], w);
    int bigC = -1, bigW = -1;
    for(auto &i: adj[u]) {
        int v = i.fi;
        if (v == p) continue;
        if (bigC == -1 || sz[bigC] < sz[v]) {
            bigC = v;
            bigW = i.se;
        }
    }
    if (bigC == -1) {
        tout[u] = timer;
        return;
    }
    hld(bigC, u, top, bigW);
    for(auto &i: adj[u]) {
        int v = i.fi;
        if (v == p || v == bigC) continue;
        hld(v, u, v, i.se);
    }
    tout[u] = timer;
}
void update(int u, int v, int c) {
    while(head[u] != head[v]) {
        if (high[head[u]] < high[head[v]]) swap(u, v);
        it.update(tin[head[u]], tin[u], c);
        u = par[head[u]];
    }
    if (high[u] > high[v]) swap(u, v);
    it.update(tin[u], tin[v], c);
}
long long get(int u, int v) {
    // if (high[u] < high[v]) swap(u, v);
    long long ans = INF;
    // cerr << "DB: " << u << ' ' << v << endl;
    while(head[u] != head[v]) {
        if (high[head[u]] < high[head[v]]) swap(u, v);
        // cerr << it.get(tin[head[u]], tin[u]) << endl;
        ans = min(ans, it.get(tin[head[u]], tin[u]));
        // ans += weight.get(tin[head[u]], tin[u]);
        // cerr << head[u] << ' ' << u << endl;
        u = par[head[u]]; 
    }
    if (high[u] > high[v]) swap(u, v);
    ans = min(ans, it.get(tin[u], tin[v]));
    // ans += weight.get(tin[u] + 1, tin[v]);
    return ans;
}
long long calF(int u, int p) {
    f1[u] = f2[u] = {INF, 0};
    if (isShop[u]) f1[u] = {0, u};
    for(auto &i: adj[u]) {
        int v = i.fi, c = i.se;
        if (v == p) continue;
        long long val = calF(v, u) + c;
        if (f1[u].fi > val) {
            f2[u] = f1[u];
            f1[u] = mp(val, v);
        }
        else {
            if (minimize(f2[u].fi, val)) f2[u].se = v;
        }
    }
    // cerr << u << ' ' << f1[u].fi << ' ' << f1[u].se << endl;
    return f1[u].fi;
}

void calQuery(int u, int p) {
    for(auto [v, id]: queries[u]) {
        ans[id] = f1[u].fi;
        ans[id] = min(ans[id], get(v, u));
    }
    for(auto [v, c]: adj[u]) {
        if (v == p) continue;
        if (f1[u].fi == 0) {
            // cerr << u << endl;
            it.update1(tin[u], 0);
            // cerr << u << ' ' << v << ' ' << 0 << endl;
        }
        else {
            if (v == f1[u].se) {
                it.update1(tin[u], f2[u].fi);
                // cerr << u << ' ' << v << ' ' << f2[u].fi << endl;
            }
            else {
                it.update1(tin[u], f1[u].fi);
                // cerr << u << ' ' << v << ' ' << f1[u].fi << endl;
            }
        }
        update(root, u, c);
        calQuery(v, u);
        update(root, u, -c);
        // cerr << -c << endl;
    }
}
void solve() {
    fw = Fenwick(n);
    dfs(root, -1);
    hld(root, -1, root, 0);
    for(int shop: shops) fw.update(tin[shop], 1);
    for(int i = 1; i <= q; i++) {
        int road, node; cin >> road >> node;
        int u = e[road].fi, v = e[road].se;
        if (high[u] > high[v]) swap(u, v);
        if (isChild(node, v)) {
            if (fw.get(tin[v], tout[v]) == 0) {
                // cout << "oo\n";
                ans[i] = INF;
                continue;
            }
            if (numShop == n) {
                ans[i] = 0;
                // cout << 0 << endl;
                continue;
            }
            queries[node].push_back({v, i});
            // long long ans = INF;
            // for(int shop: shops) if (isChild(shop, v)) {
            //     ans = min(ans, get(shop, node));
            // }
            // cout << ans << endl;
        }
        else {
            // cout << "escaped\n";
            ans[i] = -1;
        }
    }
    calF(root, -1);
    // for(int i = 1; i <= n; i++) cout << f1[i].fi << ' ' << f1[i].se << ' ' << f2[i].fi << ' ' << f2[i].se << endl;
    // cerr << f1[3].fi << ' ' << f1[3].se << endl;
    it = SegTree(n);
    calQuery(root, -1);
    for(int i = 1; i <= q; i++) {
        if (ans[i] == INF) cout << "oo";
        else if (ans[i] == -1) cout << "escaped";
        else cout << ans[i];
        cout << endl;
    }
}
signed main() {
    ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
    if (fopen(TASK".inp", "r")) {
        freopen(TASK".inp", "r", stdin);
        freopen(TASK".out", "w", stdout);
    }
    int test = 1;
    // cin >> test;
    while(test--) {
        read();
        solve();
    }
    return 0;
}

Compilation message (stderr)

valley.cpp: In function 'int main()':
valley.cpp:284:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  284 |         freopen(TASK".inp", "r", stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
valley.cpp:285:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  285 |         freopen(TASK".out", "w", stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~

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