Submission #197768

#	Time	Username	Problem	Language	Result	Execution time	Memory
197768		DS007	Election Campaign (JOI15_election_campaign)	C++14	10 / 100	474 ms	35896 KiB

election_campaign

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

struct query {
    int a, b, c;
};

const int N = 1e5;
vector<int> adj[N];
long long subtree[N], dp[N];
vector<query> q;
bool check[N];
int parent[N];
int n, m;

vector<int> euler, depth;
int first[N], last[N];
int c = 0;

int sparse[N * 2][18];
long long t[N * 8];

void dfs(int v, int p = -1, int d = 0) {
    first[v] = c++;
    parent[v] = p;
    euler.push_back(v);
    depth.push_back(d);

    for (int i : adj[v]) {
        if (i != p) {
            dfs(i, v, d + 1);
            euler.push_back(v);
            depth.push_back(d);
            c++;
        }
    }

    last[v] = c - 1;
}

int merge(int a, int b) {
    return depth[a] < depth[b] ? a : b;
}

void build_sparse() {
    for (int i = 0; i < euler.size(); i++)
        sparse[i][0] = i;

    for (int i = 1; i <= log2(n); i++) {
        for (int j = 0; j < euler.size() && j - 1 + (1 << i) < euler.size(); j++)
            sparse[j][i] = merge(sparse[j][i - 1], sparse[j + (1 << (i - 1))][i - 1]);
    }
}

int query_lca(int u, int v) {
    if (u == v) return u;
    int f1 = min(first[u], first[v]), f2 = max(first[v], first[u]), diff = f2 - f1;
    int dx = log2(diff);
    return euler[merge(sparse[f1][dx], sparse[f2 + 1 - (1 << dx)][dx])];
}

bool cmp(query u, query v) {
    int lca1 = query_lca(u.a, u.b), lca2 = query_lca(v.a, v.b);
    if (depth[first[lca1]] == depth[first[lca2]])
        return lca1 < lca2;
    return depth[first[lca1]] < depth[first[lca2]];
}

long long query_tree(int v, int l, int r, int tl, int tr) {
    if (tl > tr)
        return 0;
    else if (l == tl && r == tr)
        return t[v];

    int mid = (l + r) / 2;
    return query_tree(v * 2, l, mid, tl, min(mid, tr)) + query_tree(v * 2 + 1, mid + 1, r, max(tl, mid + 1), tr);
}

void update(int v, int l, int r, int tl, long long val) {
    if (l == r && l == tl) {
        t[v] = val;
        return;
    }

    int mid = (l + r) / 2;
    if (tl <= mid)
        update(v * 2, l, mid, tl, val);
    else
        update(v * 2 + 1, mid + 1, r, tl, val);

    t[v] = t[v * 2] + t[v * 2 + 1];
}

long long calc(int v, int p) {
    if (check[v])
        return dp[v];

    for (int i : adj[v]) {
        if (i != p)
            subtree[v] += calc(i, v);
    }
    dp[v] = subtree[v];

    check[v] = true;
    return dp[v];
}

long long solve(query u) {
    int lca = query_lca(u.a, u.b);
    if (!check[lca]) {
        calc(lca, parent[lca]);
    }

    long long sum = query_tree(1, 0, euler.size() - 1, first[lca], first[u.a]) + query_tree(1, 0, euler.size() - 1, first[lca], first[u.b]) + 2 * (dp[lca] - subtree[lca]) + subtree[lca] + u.c;
    if (sum > dp[lca]) {
        dp[lca] = sum;
        update(1, 0, euler.size() - 1, first[lca], subtree[lca] - dp[lca]);
        if (lca != 0)
            update(1, 0, euler.size() - 1, last[lca] + 1, dp[lca] - subtree[lca]);
    }

    assert(sum >= 0);
    return sum;
}

signed main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    cout.tie(nullptr);

    cin >> n;
    for (int i = 0; i < n - 1; i++) {
        int x, y;
        cin >> x >> y;
        x--, y--;
        adj[x].push_back(y);
        adj[y].push_back(x);
    }

    cin >> m;
    for (int i = 0; i < m; i++) {
        int a, b, c;
        cin >> a >> b >> c;
        a--, b--;
        q.push_back({a, b, c});
    }

    dfs(0);
    build_sparse();
    // for (int i = 0; i < m; i++) cout << query_lca(q[i].a, q[i].b) << endl;
    sort(q.begin(), q.end(), &cmp);
    reverse(q.begin(), q.end());

    long long ans = 0;
    for (query i : q) {
        ans = max(ans, solve(i));
    }
    cout << ans;
}

Compilation message (stderr)

election_campaign.cpp: In function 'void build_sparse()':
election_campaign.cpp:46:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for (int i = 0; i < euler.size(); i++)
                     ~~^~~~~~~~~~~~~~
election_campaign.cpp:50:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         for (int j = 0; j < euler.size() && j - 1 + (1 << i) < euler.size(); j++)
                         ~~^~~~~~~~~~~~~~
election_campaign.cpp:50:62: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         for (int j = 0; j < euler.size() && j - 1 + (1 << i) < euler.size(); j++)
                                             ~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~

• Subtask 1: 0 / 10
• Subtask 2: 5 / 5
• Subtask 3: 5 / 5
• Subtask 4: 0 / 30
• Subtask 5: 0 / 10
• Subtask 6: 0 / 40