Submission #520951

#	Time	Username	Problem	Language	Result	Execution time	Memory
520951		Alex_tz307	Jakarta Skyscrapers (APIO15_skyscraper)	C++17	57 / 100	1095 ms	95552 KiB

skyscraper

#include <bits/stdc++.h>
#define INF 0x3f3f3f3f

using namespace std;

void minSelf(int &x, int y) {
  if (y < x) {
    x = y;
  }
}

void testCase() {
  int n, m;
  cin >> n >> m;
  vector<vector<int>> g(n);
  int source = 0, sink = 0;
  for (int i = 0; i < m; ++i) {
    int b, p;
    cin >> b >> p;
    if (0 <= b - p || b + p < n) {
      g[b].emplace_back(p);
    }
    if (i == 0) {
      source = b;
    }
    if (i == 1) {
      sink = b;
    }
  }
  if (source == sink) {
    cout << "0\n";
    return;
  }
  for (int v = 0; v < n; ++v) {
    sort(g[v].begin(), g[v].end());
    g[v].erase(unique(g[v].begin(), g[v].end()), g[v].end());
  }
  queue<tuple<int, int, int>> q;
  unordered_set<int> vis;
  vector<bool> mark(n);
  int best = INF;
  auto convert = [&](int x, int y) -> int {
    return x * n + y;
  };
  for (int p : g[source]) {
    q.emplace(0, source, p);
    vis.emplace(convert(source, p));
    mark[0] = true;
  }
  while (!q.empty()) {
    int cost, u, p;
    tie(cost, u, p) = q.front();
    q.pop();
    if (u == sink) {
      minSelf(best, cost);
    }
    if (!mark[u]) {
      for (int pp : g[u]) {
        int state = convert(u, pp);
        if (!vis.count(state)) {
          vis.emplace(state);
          q.emplace(cost, u, pp);
        }
      }
      mark[u] = true;
    }
    for (int sgn : {-1, 1}) {
      int v = u + sgn * p;
      if (0 <= v && v < n) {
        int state = convert(v, p);
        if (!vis.count(state)) {
          vis.emplace(state);
          q.emplace(cost + 1, v, p);
        }
      }
    }
  }
  if (best == INF) {
    cout << "-1\n";
  } else {
    cout << best << '\n';
  }
}

int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(nullptr);
  int tests = 1;
  for (int tc = 0; tc < tests; ++tc) {
    testCase();
  }
  return 0;
}

• Subtask 1: 10 / 10
• Subtask 2: 12 / 12
• Subtask 3: 14 / 14
• Subtask 4: 21 / 21
• Subtask 5: 0 / 43