Submission #878991

#	Time	Username	Problem	Language	Result	Execution time	Memory
878991		12345678	Election Campaign (JOI15_election_campaign)	C++17	100 / 100	163 ms	41832 KiB

election_campaign

#include <bits/stdc++.h>

using namespace std;

const int nx=1e5+5, kx=17;

int n, m, a[nx], b[nx], c[nx], u, v, dp1[nx], dp2[nx], lvl[nx], pa[nx][kx], sm[nx];
vector<int> d[nx], l[nx];

void dfs(int u, int p)
{
    lvl[u]=lvl[p]+1;
    pa[u][0]=p;
    for (int i=1; i<kx; i++) pa[u][i]=pa[pa[u][i-1]][i-1];
    for (auto v:d[u]) if (v!=p) dfs(v, u);
}

int lca(int u, int v)
{
    if (lvl[u]>lvl[v]) swap(u, v);
    for (int i=kx-1; i>=0; i--) if (lvl[pa[v][i]]>=lvl[u]) v=pa[v][i];
    if (u==v) return v;
    for (int i=kx-1; i>=0; i--) if (pa[u][i]!=pa[v][i]) u=pa[u][i], v=pa[v][i];
    return pa[u][0];
}

void dfs2(int u, int p)
{
    for (auto v:d[u]) if (v!=p) dfs2(v, u), dp2[u]+=dp1[v];
    dp1[u]=dp2[u];
    for (auto i:l[u])
    {
        int tmp=dp2[u], x, tmp2=0;
        stack<int> s;
        while (a[i]!=u) s.push(a[i]), a[i]=pa[a[i]][0];
        while (!s.empty()) x=s.top(), s.pop(), tmp2+=sm[x], sm[x]=tmp2, pa[x][0]=u;
        tmp+=tmp2; tmp2=0;
        while (b[i]!=u) s.push(b[i]), b[i]=pa[b[i]][0];
        while (!s.empty()) x=s.top(), s.pop(), tmp2+=sm[x], sm[x]=tmp2, pa[x][0]=u;
        dp1[u]=max(dp1[u], tmp+tmp2+c[i]); 
    }
    sm[u]=dp2[u]-dp1[u];
    //cout<<u<<' '<<dp1[u]<<' '<<dp2[u]<<' '<<sm[u]<<'\n';
}

int main()
{
    cin.tie(NULL)->sync_with_stdio(false);
    cin>>n;
    for (int i=1; i<n; i++) cin>>u>>v, d[u].push_back(v), d[v].push_back(u);
    dfs(1, 1);
    cin>>m;
    for (int i=1; i<=m; i++) cin>>a[i]>>b[i]>>c[i], l[lca(a[i], b[i])].push_back(i);
    dfs2(1, 1);
    cout<<dp1[1];
}

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