Submission #365005

#	Time	Username	Problem	Language	Result	Execution time	Memory
365005		tatyam	Swapping Cities (APIO20_swap)	C++17	100 / 100	456 ms	23660 KiB

swap

#include <bits/stdc++.h>
using namespace std;

struct UnionFind{
    vector<vector<pair<int, int>>> data;
    vector<int> flag_time, degree;
    UnionFind(int n = 0): data(n, {{-1, -1}}), flag_time(n, INT_MAX), degree(n){}
    int merged_time(int x) const {
        const auto [time, root] = data[x].back();
        if(root < 0) return INT_MAX;
        return time;
    }
    int root(int t, int x) const { // after t
        if(t < merged_time(x)) return x;
        return root(t, data[x].back().second);
    }
    bool unite(int t, int x, int y){
        bool flag = ++degree[x] >= 3 || ++degree[y] >= 3;
        x = root(t, x);
        y = root(t, y);
        if(x == y){
            if(flag_time[x] == INT_MAX) flag_time[x] = t;
            return 0;
        }
        const int size_x = data[x].back().second, size_y = data[y].back().second;
        if(size_x > size_y) swap(x, y);
        if(flag_time[x] == INT_MAX && (flag || flag_time[y] != INT_MAX)) flag_time[x] = t;
        data[x].emplace_back(t, size_x + size_y);
        data[y].emplace_back(t, x);
        return 1;
    }
} uf;
vector<array<int, 3>> edge;

void init(int N, int M, vector<int> U, vector<int> V, vector<int> W){
    uf = UnionFind(N);
    edge.resize(M);
    for(int i = 0; i < M; i++) edge[i] = {U[i], V[i], W[i]};
    sort(edge.begin(), edge.end(), [&](const auto& a, const auto& b){ return a[2] < b[2]; });
    for(int i = 0; i < M; i++){
        const auto& [U, V, W] = edge[i];
        uf.unite(i + 1, U, V);
    }
}

int getMinimumFuelCapacity(int X, int Y){
    auto check = [&](int t){
        const int x = uf.root(t, X), y = uf.root(t, Y);
        return x == y && uf.flag_time[x] <= t;
    };
    int ng = 0, ok = edge.size();
    if(!check(ok)) return -1;
    while(ok - ng > 1){
        const int cen = (ok + ng) / 2;
        (check(cen) ? ok : ng) = cen;
    }
    return edge[ok - 1][2];
}

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