Submission #1283950

#	Time	Username	Problem	Language	Result	Execution time	Memory
1283950		hungdt	Construction of Highway (JOI18_construction)	C++20	7 / 100	2095 ms	64668 KiB

construction

#include <bits/stdc++.h>

using namespace std;

const int maxn = 4005;
int a[maxn];
vector<int> adj[maxn];
int par[maxn];
int h[maxn];
int n;
int inv[maxn];
vector<pair<int, int>> q;
int fen[maxn][maxn];
vector<int> comp;
vector<int> way[maxn];
int ans;

void compress(){
    for (int i=1; i<=n; i++) comp.push_back(a[i]);

    sort(comp.begin(), comp.end());

    for (int i=1; i<=n; i++) a[i] = lower_bound(comp.begin(), comp.end(), a[i]) - comp.begin() + 1;
}

void findpar(int node, int parent){
    h[node] = h[parent] + 1;
    par[node] = parent;
    for (int x: way[parent]) way[node].push_back(x);
    way[node].push_back(node);
    for (int x: adj[node]){
        if (x != parent){
            findpar(x, node);
        }
    }
}

void update(int node, int val){
    while (node != 1){
        a[node] = val;
        node = par[node];
    }

    a[1] = val;
}

void updatefen(int index, int t){
    while (index <= comp.size()){
        fen[t][index]++;
        index += (index & (-index));
    }
}

int queryfen(int index, int t){
    int res = 0;
    while (index > 0){
        res += fen[t][index];
        index -= (index & (-index));
    }

    return res;
}

void build(int node){
    for (int i=1; i<=n; i++) fen[node][i] = 0;
    for (int x: way[node]){
        updatefen(a[x], node);
    }

    inv[node] = inv[par[node]] + queryfen(comp.size(), node) - queryfen(a[node], node);
}

void dfs(int node){
    build(node);
    for (int x: adj[node]){
        if (x == par[node]) continue;
        dfs(x);
    }
}

int main()
{
    ios_base :: sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);

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

    compress();
    findpar(1, 0);
    dfs(1);

    for (int i=0; i<n-1; i++){
        int x = q[i].first, y = q[i].second;
        if (h[x] > h[y]) swap(x, y);
        cout << inv[x] << '\n';
        update(y, a[y]);
        dfs(1);
    }

    return 0;
}

• Subtask 1: 7 / 7
• Subtask 2: 0 / 9
• Subtask 3: 0 / 84