Submission #767993

#	Time	Username	Problem	Language	Result	Execution time	Memory
767993		boris_mihov	Ideal city (IOI12_city)	C++17	32 / 100	1061 ms	8268 KiB

city

#include <algorithm>
#include <iostream>
#include <numeric>
#include <cassert>
#include <vector>
#include <queue>
#include <map>

typedef long long llong;
const int MAXN = 100000 + 10;
const int MOD = 1'000'000'000;

int n;
llong ans;
int sz[MAXN];
int par[MAXN];
llong dp[MAXN];
int x[MAXN], y[MAXN];
std::pair <int,int> delta[] = {{-1, 0}, {0, -1}, {1, 0}, {0, 1}};
std::map <std::pair <int,int>, int> map;
std::vector <int> g[MAXN];
std::vector <int> t[MAXN];
std::queue <int> q;

void dfsDown(int node)
{
    dp[node] = 0;
    sz[node] = 1;

    for (const int &u : t[node])
    {
        if (u == par[node])
        {
            continue;
        }
        
        dfsDown(u);
        sz[node] += sz[u];
        dp[node] += dp[u] + sz[u];
    }
}

void dfsUp(int node)
{
    std::vector <std::pair <int*, int>> rollback;
    if (node != 1)
    {
        dp[node] = dp[par[node]] + n - 2 * sz[node];
        // std::cout << "here: " << node << ' ' << par[node] << ' ' << dp[par[node]] << ' ' << sz[node] << ' ' << dp[node] << '\n';
        for (const int &u : g[node])
        {
            if (par[u] != node)
            {
                rollback.push_back({&par[u], par[u]});
                if (u != par[node] && par[par[u]] == par[node]) dp[node] -= sz[u];
                par[u] = node;
            }
        }
    }
    
    for (const int &u : t[node])
    {
        if (u != par[node])
        {
            dfsUp(u);
        }
    }

    for (auto [addr, val] : rollback)
    {
        *addr = val;
    }
}

int DistanceSum(int N, int *X, int *Y) 
{
    n = N;
    for (int i = 1 ; i <= n ; ++i)
    {
        x[i] = X[i - 1];
        y[i] = Y[i - 1];
        map[{x[i], y[i]}] = i;
    }

    for (int i = 1 ; i <= n ; ++i)
    {
        for (const auto &[dx, dy] : delta)
        {
            if (map.count({x[i] + dx, y[i] + dy}))
            {
                g[i].push_back(map[{x[i] + dx, y[i] + dy}]);
            }
        }
    }

    for (int root = 1 ; root <= n ; ++root)
    {
        q.push(root);
        std::fill(par + 1, par + n + 1, -1);
        par[root] = 0;

        for (int i = 1 ; i <= n ; ++i)
        {
            t[i].clear();
        }

        while (!q.empty())
        {
            int top = q.front();
            q.pop();

            for (const int &i : g[top])
            {
                if (par[i] == -1)
                {
                    par[i] = top;
                    t[top].push_back(i);
                    q.push(i);
                }
            }
        }

        dfsDown(root);
        // std::cout << "dp: " << root << ' ' << x[root] << ' ' << y[root] << " = " << dp[root] << '\n';
        ans += dp[root];
        ans %= MOD;
    }

    return ans / 2;
}

• Subtask 1: 11 / 11
• Subtask 2: 21 / 21
• Subtask 3: 0 / 23
• Subtask 4: 0 / 45