Submission #672916

#	Time	Username	Problem	Language	Result	Execution time	Memory
672916		vuavisao	Roadside Advertisements (NOI17_roadsideadverts)	C++14	30 / 100	34 ms	12016 KiB

roadsideadverts

#include<bits/stdc++.h>
#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")
#define ll long long
using namespace std;

const int N = 5e4 + 10;

int n, q;
vector<pair<int, int>> g[N];

int Lg, dist[N], parent[20][N];
int s_dist[N];

int cnt, in[N], out[N];

void dfs(int u);
void dfs(int u) {
    in[u] = ++ cnt;
    for(const auto& psy : g[u]) {
        int v = psy.first, w = psy.second;
        if(v == parent[0][u]) continue;
        parent[0][v] = u;
        dist[v] = dist[u] + 1;
        s_dist[v] = s_dist[u] + w;
        dfs(v);
    }
    out[u] = cnt;
}

int lca(int u, int v);
int lca(int u, int v) {
    if(dist[u] < dist[v]) swap(u, v);
    int delta = dist[u] - dist[v];
    for(int i = Lg; i >= 0; -- i) {
        if(delta >> i & 1) u = parent[i][u];
    }
    if(u == v) return u;
    for(int i = Lg; i >= 0; -- i) {
        if(parent[i][u] == parent[i][v]) continue;
        u = parent[i][u];
        v = parent[i][v];
    }
    return parent[0][u];
}

int32_t main() {
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    if (fopen("NOI17_roadsideadverts.inp", "r")) {
        freopen("NOI17_roadsideadverts.inp", "r", stdin);
        freopen("NOI17_roadsideadverts.out", "w", stdout);
    }
    cin >> n;
    for(int i = 2; i <= n; ++ i) {
        int u, v, w; cin >> u >> v >> w;
        ++ u, ++ v;
        g[u].push_back(make_pair(v, w));
        g[v].push_back(make_pair(u, w));
    }
    dfs(1);
    Lg = __lg(n);
    for(int j = 1; j <= Lg; ++ j) {
        for(int i = 1; i <= n; ++ i) {
            parent[j][i] = parent[j - 1][parent[j - 1][i]];
        }
    }
    cin >> q;
    while(q-- > 0) {
        int u[5];
        for(int i = 0; i < 5; ++ i) {
            cin >> u[i]; ++ u[i];
        }
        sort(u + 0, u + 5, [&] (int lhs, int rhs) {
            return in[lhs] > in[rhs];
        });
        auto inside = [&] (int u, int v) {
            /// u inside v
            return in[v] <= in[u] && out[u] <= out[v];
        };
        int res = 0;
        stack<int> stk = {};
        for(int i = 0; i < 5; ++ i) {
            while(!stk.empty() && inside(stk.top(), u[i])) {
                res += s_dist[stk.top()] - s_dist[u[i]];
                stk.pop();
            }
            stk.push(u[i]);
        }
        if((int) stk.size() > 1) {
            int last = 0;
            while(!stk.empty()) {
                if(last == 0) {
                    int u = stk.top(); stk.pop();
                    int v = stk.top(); stk.pop();
                    int anc = lca(u, v);
                    res += s_dist[u] + s_dist[v] - 2 * s_dist[anc];
//                    cerr << u << ' ' << v << '\n';
                    last = anc;
                }
                else {
                    int v = stk.top(); stk.pop();
                    int anc = lca(last, v);
                    res += s_dist[last] + s_dist[v] - 2 * s_dist[anc];
                    last = anc;
                }
            }
        }
        cout << res << '\n';
    }
    return 0;
}

/// Code by vuavisao

Compilation message (stderr)

roadsideadverts.cpp: In function 'int32_t main()':
roadsideadverts.cpp:52:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   52 |         freopen("NOI17_roadsideadverts.inp", "r", stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
roadsideadverts.cpp:53:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   53 |         freopen("NOI17_roadsideadverts.out", "w", stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 7 / 7
• Subtask 2: 23 / 23
• Subtask 3: 0 / 40
• Subtask 4: 0 / 30