Submission #398041

#	Time	Username	Problem	Language	Result	Execution time	Memory
398041		Charis02	Election Campaign (JOI15_election_campaign)	C++14	100 / 100	515 ms	65192 KiB

election_campaign

/*

https://oj.uz/problem/view/JOI15_election_campaign

100 points sol
*/

#include<iostream>
#include<vector>
#include<string.h>
#define ll long long
#define pi pair < ll,ll >
#define mp(a,b) make_pair(a,b)
#define MAX_N 200004

using namespace std;

vector < int > graph[MAX_N];
vector < pair < pi,ll > > tours[MAX_N];
ll jump_memo[MAX_N][21];
ll tin[MAX_N],tout[MAX_N],cur_time;
ll dp[MAX_N],S[MAX_N];
ll seg[4*MAX_N];
int n,m;

int jump(int x,int i) // find 2^i -th ancestor of x
{
    if(jump_memo[x][i] != -1)
        return jump_memo[x][i];
    return jump_memo[x][i] = jump(jump(x,i-1),i-1);
}

bool is_ancestor(int x,int y) // returns if x is ancestor of y
{
    return (tin[x] <= tin[y] && tout[x] >= tout[y]);
}

int get_lca(int x,int y)
{
    if(is_ancestor(x,y))
        return x;
    if(is_ancestor(y,x))
        return y;

    for(int i = 20;i >= 0;i--)
    {
        if(!is_ancestor(jump(x,i),y))
            x = jump(x,i);
    }

    return jump(x,0);
}

void dfs(int cur,int par)
{
    tin[cur] = cur_time++;
    jump_memo[cur][0] = par;

    for(int i = 0;i < graph[cur].size();i++)
    {
        int v = graph[cur][i];
        if(v == par)
            continue;
        dfs(v,cur);
    }

    tout[cur] = cur_time++;
    return;
}

void initialize()
{
    memset(jump_memo,-1,sizeof jump_memo);
    memset(dp,-1,sizeof dp);
    dfs(1,1);

    return;
}

void input()
{
    int a,b,c;

    cin >> n;

    for(int i = 0;i < n-1;i++)
    {
        cin >> a >> b;
        graph[a].push_back(b);
        graph[b].push_back(a);
    }

    initialize();
    cin >> m;

    for(int i = 0;i < m;i++)
    {
        cin >> a >> b >> c;
        tours[get_lca(a,b)].push_back(mp(mp(a,b),c));
    }

    return;
}

void update(int low,int high,int pos,int slow,int val)
{
    if(low == high && low == slow)
    {
        seg[pos] = val;
        return;
    }
    if(low>slow||high<slow)
        return;

    int mid = (low+high)/2;

    update(low,mid,pos*2+1,slow,val);
    update(mid+1,high,pos*2+2,slow,val);

    seg[pos] = seg[pos*2+1]+seg[pos*2+2];
    return;
}

ll query(int low,int high,int pos,int slow,int shigh)
{
    if(low >= slow && high <= shigh)
        return seg[pos];
    if(low>shigh || high < slow)
        return 0;

    int mid = (low+high)/2;

    return query(low,mid,pos*2+1,slow,shigh) + query(mid+1,high,pos*2+2,slow,shigh);
}

ll go(int cur,int target) // get value to add on path cur->target
{
    return query(0,2*n,0,tin[cur],tin[target])+S[target];
}

ll calc(int cur,int par)
{
    if(dp[cur] != -1)
        return dp[cur];

    for(int i = 0;i < graph[cur].size();i++)
    {
        int v = graph[cur][i];
        if(v==par)
            continue;

        S[cur] += calc(v,cur); // S = sum of dp of children
    }

    dp[cur] = S[cur]; // for now. dp[cur] = S[cur] if we don't do a tour on cur

    for(int i = 0;i < graph[cur].size();i++)
    {
        int v = graph[cur][i];
        if(v==par)
            continue;

        update(0,2*n,0,tin[v],S[cur]-dp[v]);  // we hold this value to utilize it in the go function. look at O(NM) implementation
        update(0,2*n,0,tout[v],-S[cur]+dp[v]); // we add opposite value, to get path sum
    }

    for(int i = 0;i < tours[cur].size();i++)
    {
        int x = tours[cur][i].first.first; // first endpoint
        int y = tours[cur][i].first.second; // second endpoint
        int C = tours[cur][i].second; // gain of tour

        dp[cur] = max(dp[cur],go(cur,x)+go(cur,y) - S[cur] + C); // S[cur] is counted twice
    }

    return dp[cur];
}

void solve()
{
    cout << calc(1,1) << endl;

    return;
}

int main()
{
    input(); // read input and initialize tree
    solve(); // solve problem

    return 0;
}

Compilation message (stderr)

election_campaign.cpp: In function 'void dfs(int, int)':
election_campaign.cpp:59:21: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   59 |     for(int i = 0;i < graph[cur].size();i++)
      |                   ~~^~~~~~~~~~~~~~~~~~~
election_campaign.cpp: In function 'long long int calc(int, int)':
election_campaign.cpp:146:21: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
  146 |     for(int i = 0;i < graph[cur].size();i++)
      |                   ~~^~~~~~~~~~~~~~~~~~~
election_campaign.cpp:157:21: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
  157 |     for(int i = 0;i < graph[cur].size();i++)
      |                   ~~^~~~~~~~~~~~~~~~~~~
election_campaign.cpp:167:21: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::pair<std::pair<long long int, long long int>, long long int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
  167 |     for(int i = 0;i < tours[cur].size();i++)
      |                   ~~^~~~~~~~~~~~~~~~~~~

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