Submission #978216

#	Time	Username	Problem	Language	Result	Execution time	Memory
978216		guagua0407	Election Campaign (JOI15_election_campaign)	C++17	100 / 100	121 ms	31400 KiB

election_campaign

//#pragma GCC optimize("O3")
#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define pii pair<int,int>
#define f first
#define s second
#define all(x) x.begin(),x.end()
#define _ ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);

int dx[4]={0,0,1,-1};
int dy[4]={1,-1,0,0};

void setIO(string s) {
    freopen((s + ".in").c_str(), "r", stdin);
    freopen((s + ".out").c_str(), "w", stdout);
}

struct node{
    int c1,c2,val;
};

const int mxn=1e5+5;
vector<int> adj[mxn];
int up[mxn][20];
int depth[mxn];
vector<node> st[mxn];
int L[mxn],R[mxn];
ll bit[mxn];
ll dp[mxn];
int cnt=0;

void update(int pos,ll val){
    for(;pos<mxn;pos+=(pos&-pos)){
        bit[pos]+=val;
    }
}

ll query(int pos){
    ll ans=0;
    for(;pos>0;pos-=(pos&-pos)){
        ans+=bit[pos];
    }
    return ans;
}

void dfs(int v,int p=0){
    up[v][0]=p;
    depth[v]=depth[p]+1;
    L[v]=++cnt;
    for(auto u:adj[v]){
        if(u==p) continue;
        dfs(u,v);
    }
    R[v]=cnt;
}

int go(int x,int len){
    for(int i=0;i<20;i++){
        if(len&(1<<i)){
            x=up[x][i];
        }
    }
    return x;
}

int lca(int a,int b){
    if(depth[a]<depth[b]) swap(a,b);
    int len=depth[a]-depth[b];
    a=go(a,len);
    if(a==b) return a;
    for(int i=19;i>=0;i--){
        int ta=up[a][i];
        int tb=up[b][i];
        if(ta!=tb){
            a=ta;
            b=tb;
        }
    }
    return up[a][0];
}

void dfs2(int v,int p=0){
    ll sum=0;
    for(auto u:adj[v]){
        if(u==p) continue;
        dfs2(u,v);
    }
    for(auto u:adj[v]){
        if(u==p) continue;
        update(L[v],dp[u]);
        update(R[v]+1,-dp[u]);
        update(L[u],-dp[u]);
        update(R[u]+1,dp[u]);
        sum+=dp[u];
    }
    dp[v]=sum;
    for(auto u:st[v]){
        dp[v]=max(dp[v],query(L[u.c1])+query(L[u.c2])-(u.c2!=0?sum:0)+u.val);
    }
    //cout<<v<<' '<<dp[v]<<'\n';
}

int main() {_
    int n;
    cin>>n;
    for(int i=0;i<n-1;i++){
        int a,b;
        cin>>a>>b;
        adj[a].push_back(b);
        adj[b].push_back(a);
    }
    dfs(1);
    for(int j=1;j<20;j++){
        for(int i=1;i<=n;i++){
            up[i][j]=up[up[i][j-1]][j-1];
        }
    }
    int q;
    cin>>q;
    for(int i=0;i<q;i++){
        int a,b,c;
        cin>>a>>b>>c;
        int node=lca(a,b);
        //cout<<node<<' '<<a<<' '<<b<<'\n';
        if(depth[a]>depth[b]) swap(a,b);
        int len=depth[b]-depth[a];
        if(a==node){
            st[node].push_back({b,0,c});
        }
        else{
            st[node].push_back({a,b,c});
        }
    }
    dfs2(1);
    cout<<dp[1]<<'\n';
    return 0;
}
//maybe its multiset not set
//yeeorz
//laborz

Compilation message (stderr)

election_campaign.cpp: In function 'int main()':
election_campaign.cpp:127:13: warning: unused variable 'len' [-Wunused-variable]
  127 |         int len=depth[b]-depth[a];
      |             ^~~
election_campaign.cpp: In function 'void setIO(std::string)':
election_campaign.cpp:15:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   15 |     freopen((s + ".in").c_str(), "r", stdin);
      |     ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
election_campaign.cpp:16:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   16 |     freopen((s + ".out").c_str(), "w", stdout);
      |     ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

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