Submission #859661

#	Time	Username	Problem	Language	Result	Execution time	Memory
859661		boris_mihov	Road Closures (APIO21_roads)	C++17	0 / 100	20 ms	5288 KiB

roads

#include "roads.h"
#include <algorithm>
#include <iostream>
#include <numeric>
#include <cassert>
#include <vector>

typedef long long llong;
const int MAXN = 2000 + 10;
const llong INF = 1e18;
const int INTINF = 1e9;

int n;
std::vector <std::pair <int,int>> g[MAXN];
bool bl[MAXN][2][2];
llong dp[MAXN][2][2];

void firstDFS(int node, int par)
{
    for (auto &curr : g[node])
    {
        if (curr.first == par)
        {
            std::swap(curr, g[node].back());
            g[node].pop_back();
            break;
        }
    }

    for (const auto &[u, w] : g[node])
    {
        firstDFS(u, node);
    }
}

llong f(int node, int k, bool k2)
{
    // if (k == 1) std::cout << "call: " << node << ' ' << g[node].size() << ' ' << k << '\n';
    if (g[node].empty())
    {
        return 0;
    }

    if (bl[node][k][k2])
    {
        return dp[node][k][k2];
    }

    bl[node][k][k2] = true;
    std::vector <std::pair <llong,int>> vals;
    for (const auto &[u, w] : g[node])
    {
        dp[node][k][k2] += w + f(u, k + k2, false);
        vals.push_back({f(u, k + k2 - 1, true) - (w + f(u, k + k2, false)), u});
    }

    std::sort(vals.begin(), vals.end());
    for (int i = 0 ; i < std::min((int)vals.size(), k) ; ++i)
    {
        if (vals[i].first >= 0) break;
        dp[node][k][k2] += vals[i].first;
    }

    return dp[node][k][k2];
}

std::vector <llong> minimum_closure_costs(int N, std::vector <int> U, std::vector <int> V, std::vector <int> W)
{
    n = N;
    for (int i = 0 ; i < n - 1 ; ++i)
    {
        g[U[i] + 1].push_back({V[i] + 1, W[i]});
        g[V[i] + 1].push_back({U[i] + 1, W[i]});
    }

    std::sort(W.begin(), W.end(), std::greater <int> ());
    std::vector <llong> ans(n, 0);
    llong sum = 0;

    for (int i = n - 1 ; i >= 0 ; --i)
    {
        if (W.size() > i)
        {
            sum += W.back();
            W.pop_back();
        }

        ans[i] = sum;
    }

    return ans;
    firstDFS(1, 0);
    int cnt = 0;
    for (int i = 0 ; i <= 1 ; ++i)
    {
        ans[i] = f(1, i, false);
    }
    
    // for (int i = 1 ; i <= n ; ++i)
    // {
    //     for (int k = 0 ; k + 1 < n ; ++k)
    //     {
    //         assert(f(i, k, false) - f(i, k + 1, false) >= f(i, k + 1, false) - f(i, k + 2, false));
    //         assert(f(i, k, true) - f(i, k + 1, true) >= f(i, k + 1, true) - f(i, k + 2, true));
    //     }
    // }

    return ans;
}

Compilation message (stderr)

roads.cpp: In function 'std::vector<long long int> minimum_closure_costs(int, std::vector<int>, std::vector<int>, std::vector<int>)':
roads.cpp:82:22: warning: comparison of integer expressions of different signedness: 'std::vector<int>::size_type' {aka 'long unsigned int'} and 'int' [-Wsign-compare]
   82 |         if (W.size() > i)
      |             ~~~~~~~~~^~~
roads.cpp:93:9: warning: unused variable 'cnt' [-Wunused-variable]
   93 |     int cnt = 0;
      |         ^~~

• Subtask 1: 0 / 5
• Subtask 2: 0 / 7
• Subtask 3: 0 / 14
• Subtask 4: 0 / 10
• Subtask 5: 0 / 17
• Subtask 6: 0 / 25
• Subtask 7: 0 / 22