Submission #405951

#	Time	Username	Problem	Language	Result	Execution time	Memory
405951		tengiz05	Swapping Cities (APIO20_swap)	C++17	0 / 100	2082 ms	18564 KiB

swap

#include "swap.h"
#include <bits/stdc++.h>
constexpr int N = 1e5;
std::set<int> e[N];
std::vector<int> U, V, W;
int n, m;
void init(int n, int m, std::vector<int> U, std::vector<int> V, std::vector<int> W) {
    ::U = U;
    ::V = V;
    ::W = W;
    ::n = n;
    ::m = m;
}
std::vector<int> p;
std::vector<bool> vis;
void dfs(int u, int P) {
    p[u] = P;
    vis[u] = true;
    for (auto v : e[u]) {
        if (!vis[v]) {
            dfs(v, u);
        }
    }
}
bool check(int X, int Y, int mid) {
    for (int i = 0; i < n; i++) e[i].clear();
    for (int i = 0; i < m; i++) {
        if (W[i] <= mid) {
            e[U[i]].emplace(V[i]);
            e[V[i]].emplace(U[i]);
        }
    }
    p.assign(n, -1);
    vis.assign(n, false);
    dfs(X, -1);
    if (p[Y] == -1)
        return false;
    int y = Y;
    std::vector<int> got;
    y = p[y];
    while (y != -1 && p[y] != -1) {
        got.push_back(y);
        y = p[y];
    }
    for (auto x : got) {
        if (e[x].size() > 2) {
            return true;
        }
    }
    if (e[X].size() > 2 && e[Y].size() > 2) {
        return true;
    }
    y = Y;
    for (auto x : got) {
        e[x].erase(y);
        e[y].erase(x);
        y = x;
    }
    if (!got.size()) {
        e[X].erase(Y);
        e[Y].erase(X);
    }
    p.assign(n, -1);
    vis.assign(n, false);
    dfs(X, -1);
    if (p[Y] == -1)
        return false;
    return true;
}
int getMinimumFuelCapacity(int X, int Y) {
    int l = 0, r = 1e9 + 1;
    while (l + 1 < r) {
        int mid = (l + r) / 2;
        if (check(X, Y, mid)) {
            r = mid;
        } else {
            l = mid;
        }
    }
    if (r == 1e9 + 1) r = -1;
    return r;
}

• Subtask 1: 0 / 6
• Subtask 2: 0 / 7
• Subtask 3: 0 / 17
• Subtask 4: 0 / 20
• Subtask 5: 0 / 23
• Subtask 6: 0 / 27