Submission #975813

#	Time	Username	Problem	Language	Result	Execution time	Memory
975813		OAleksa	Swapping Cities (APIO20_swap)	C++14	100 / 100	331 ms	40760 KiB

swap

#include "swap.h"
#include <bits/stdc++.h>
#define f first
#define s second
using namespace std;
const int N = 1e5 + 69;
const int inf = 1e9 + 69;
vector<tuple<int, int, int>> edges;
int n, m, p[N], sz[N], deg[N], lan[N];
vector<pair<int, int>> par[N];
vector<int> who[N];
int root(int v) {
  if (p[v] == v)
    return v;
  return p[v] = root(p[v]);
}
void init(int _n, int _m, vector<int> u, vector<int> v, vector<int> w) {
  n = _n;
  m = _m;
  for (int i = 0;i < m;i++)
    edges.push_back({w[i], u[i], v[i]});
  sort(edges.begin(), edges.end());
  for (int i = 0;i < n;i++) {
    sz[i] = 1;
    p[i] = i;
    par[i].push_back({0, i});
    who[i].push_back(i);
    lan[i] = inf;
  }
  for (auto u : edges) {
    int c, b, a;
    tie(c, a, b) = u;
    int x = root(a);
    int y = root(b);
    if (x != y) {
      if (sz[x] < sz[y])
        swap(x, y);
      for (auto j : who[y]) {
        par[j].push_back({c, x});
        who[x].push_back(j);
      }
      p[y] = x;
      sz[x] += sz[y];
    }
  }
  for (int i = 0;i < n;i++) {
    p[i] = i;
    sz[i] = 1;
    who[i].clear();
    who[i].push_back(i);
    par[i].push_back({inf, par[i].back().s});
  }
  //lanac i lanac->lanac
  //nelanac i lanac->nelanac
  for (auto u : edges) {
    int a, b, c;
    tie(c, a, b) = u;
    int x = root(a);
    int y = root(b);
    if (x != y) {
      if (lan[x] != inf && lan[y] == inf) {
        for (auto j : who[y])
          lan[j] = c;
        who[y].clear();
      }
      else if (lan[y] != inf && lan[x] == inf) {
        for (auto j : who[x])
          lan[j] = c;
        who[x].clear();
      }
      else if (lan[x] == inf && lan[y] == inf && (deg[a] == 2 || deg[b] == 2)) {
        for (auto j : who[x])
          lan[j] = c;
        who[x].clear();
        for (auto j : who[y])
          lan[j] = c;
        who[y].clear();
      }
      if (sz[x] < sz[y])
        swap(x, y);
      for (auto j : who[y])
        who[x].push_back(j);
      sz[x] += sz[y];
      p[y] = x;
    }
    else {
      if (lan[x] != inf)
        continue;
      for (auto j : who[x])
        lan[j] = c;
      who[x].clear();
    }
    deg[a] += 1;
    deg[b] += 1;
  }
  /*
  for (int i = 0;i < n;i++)
    cout << lan[i] << ' ';*/
}

int getMinimumFuelCapacity(int x, int y) {
  int l = 1, r = 1e9, same = -1;
  auto check = [&](int mid) {
    pair<int, int> s = make_pair(mid, inf);
    auto u = upper_bound(par[x].begin(), par[x].end(), s);
    auto u1 = upper_bound(par[y].begin(), par[y].end(), s);
    int i = u - par[x].begin();
    int j = u1 - par[y].begin();
    if (i == 0 || j == 0)
      return false;
    --i, --j;
    return par[x][i].s == par[y][j].s;
  };
  while (l <= r) {
    int mid = (l + r) / 2;
    if (check(mid)) {
      same = mid;
      r = mid - 1;
    }
    else
      l = mid + 1;
  }
  int ans = max(same, max(lan[x], lan[y]));
  if (ans > 1e9)
    ans = -1;
  return ans;
}
/*
5 6
0 1 4
0 2 4
1 2 1
1 3 2
1 4 10
2 3 3
3
1 2
2 4
0 1

3 2
0 1 5
0 2 5
1
1 2

5 4
0 1 3
1 4 4
1 2 1
2 3 2
1
1 3
*/

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