Submission #1320588

#TimeUsernameProblemLanguageResultExecution timeMemory
1320588benjaminshihNestabilnost (COI23_nestabilnost)C++20
12 / 100
165 ms197452 KiB
#include <bits/stdc++.h>
using namespace std;

const int mxn = 3e5+10;
const long long INF = 1e18;

int n;
int a[mxn];
int f[mxn];
vector<int> g[mxn];
long long dp[mxn]; 
// 預處理因數,只用於 N <= 5000 的情況
vector<int> divs_list[5005]; 

void init_divs() {
    if (n > 5000) return;
    for (int i = 1; i <= n; i++) {
        for (int j = i; j <= n; j += i) {
            divs_list[j].push_back(i);
        }
    }
}

// DFS 回傳 vector,代表在不同 k 之下,如果不切斷 u,可以省多少成本
// savings[k] = dp[u] - cost_if_kept_connected_with_mod_k
vector<long long> dfs(int u, int p) {
    long long sum_child_dp = 0;
    
    // 初始化當前節點的 savings 列表
    vector<long long> my_savings;
    if (n <= 5000) my_savings.assign(n + 1, 0);

    for (int v : g[u]) {
        if (v == p) continue;
        
        // 遞迴取得子節點的 savings
        vector<long long> child_savings = dfs(v, u);
        sum_child_dp += dp[v];

        // 如果 N 很大,直接跳過合併邏輯避免 TLE (放棄 Subtask 2, 5)
        if (n > 5000) continue;

        // 合併子節點的 savings
        if (a[v] == a[u] + 1) {
            // 情況 1: 數值差 1,只要 k > a[v] 都可以連
            for (int k = a[v] + 1; k <= n; k++) {
                my_savings[k] += child_savings[k];
            }
        } else if (a[v] <= a[u]) {
            // 情況 2: 數值變小或不變,檢查因數
            int diff = a[u] + 1 - a[v];
            for (int k : divs_list[diff]) {
                if (k > a[v]) { 
                    my_savings[k] += child_savings[k];
                }
            }
        }
    }

    // 計算 dp[u]
    dp[u] = INF;
    
    if (n <= 5000) {
        for (int k = a[u] + 1; k <= n; k++) {
            // Cost = f[k] + sum(dp[child]) - sum(savings[child])
            long long cost = f[k] + sum_child_dp - my_savings[k];
            if (cost < dp[u]) dp[u] = cost;
        }
    } else {
        // N 很大時的 fallback (雖然過不了但防止 Runtime Error)
        dp[u] = sum_child_dp + f[min(n, a[u]+1)]; 
    }

    // 更新 my_savings 以回傳給父節點
    // 數學推導: S_u[k] = dp[u] - (sum_child_dp - sum_child_savings)
    //                = dp[u] - sum_child_dp + current_accumulated_savings
    if (n <= 5000) {
        long long base_diff = dp[u] - sum_child_dp;
        for (int k = 1; k <= n; k++) {
            if (k > a[u]) {
                my_savings[k] += base_diff;
            } else {
                my_savings[k] = 0; // k 不合法,無法連接,saving 為 0
            }
        }
    }
    
    return my_savings;
}

int main(){
    ios::sync_with_stdio(0); cin.tie(0);
    
    if (!(cin >> n)) return 0;
    
    init_divs();

    for(int i = 1 ; i <= n ; i++) cin >> a[i];
    for(int i = 1 ; i <= n ; i++) cin >> f[i];

    for(int i = 0 ; i < n - 1 ;  i++){
        int u, v;
        cin >> u >> v;
        g[u].push_back(v);
        g[v].push_back(u);
    }

    dfs(1, 0);

    cout << dp[1] << endl;
}
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