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Submission #501724

# Submission time Handle Problem Language Result Execution time Memory
501724 2022-01-04T12:00:21 Z 600Mihnea Islands (IOI08_islands) C++17
80 / 100
 596 ms 131076 KB 
#include <bits/stdc++.h>

using namespace std;

typedef long long ll;

struct Edge {
  int a, b, cost;
  bool seen = false;
};

const int N = (int) 1e6 + 7;
const ll INF = (ll) 1e18;
int n;
int parrent[N];
Edge graph_edges[N];
vector<int> g[N], verts;
bool vis[N];
int dep[N];
int epar[N];

void build1dfsdfs(int a) {
  vis[a] = true;
  verts.push_back(a);
  for (auto &i : g[a]) {
    int b = graph_edges[i].a + graph_edges[i].b - a;
    if (!vis[b]) {
      dep[b] = 1 + dep[a];
      epar[b] = i;
      build1dfsdfs(b);
      parrent[b] = a;
      graph_edges[i].seen = true;
    }
  }
}

vector<int> geallonp(int a, int b) {
  vector<int> p1, p2;
  while (a != b) {
    if (dep[a] > dep[b]) {
      p1.push_back(a);
      a = parrent[a];
    } else {
      p2.push_back(b);
      b = parrent[b];
    }
  }
  p1.push_back(a);
  reverse(p2.begin(), p2.end());
  for (auto &x : p2) {
    p1.push_back(x);
  }
  return p1;
}

vector<int> geallonpedges(int a, int b) {
  vector<int> p1, p2;
  while (a != b) {
    if (dep[a] > dep[b]) {
      p1.push_back(epar[a]);
      a = parrent[a];
    } else {
      p2.push_back(epar[b]);
      b = parrent[b];
    }
  }
  reverse(p2.begin(), p2.end());
  for (auto &x : p2) {
    p1.push_back(x);
  }
  return p1;
}

bool blocked[N];
ll under[N];
ll bbpath[N];

void dfs(int a, int p = -1) {
  for (auto &i : g[a]) {
    int b = graph_edges[i].a + graph_edges[i].b - a;
    if (blocked[b] || b == p) {
      continue;
    }
    dfs(b, a);
    bbpath[a] = max(bbpath[a], bbpath[b]);
    bbpath[a] = max(bbpath[a], under[b] + graph_edges[i].cost + under[a]);
    under[a] = max(under[a], under[b] + graph_edges[i].cost);
  }

}

ll sum[N];

ll solveComponent(int rootVertex) {
  ll sol = 0;
  verts.clear();
  build1dfsdfs(rootVertex);
  vector<int> nnseeng;
  for (auto &v : verts) {
    for (auto &i : g[v]) {
      if (!graph_edges[i].seen) {
        graph_edges[i].seen = true;
        nnseeng.push_back(i);
      }
    }
  }
  {
    int index = nnseeng[0];
    int a = graph_edges[index].a;
    int b = graph_edges[index].b;
    int cost = graph_edges[index].cost;
    vector<int> path = geallonp(a, b);
    vector<int> edges = geallonpedges(a, b);
    vector<ll> value;
    edges.push_back(index);


    for (auto &v : path) {
      blocked[v] = true;
    }



    for (auto &v : path) {
      dfs(v);
      sol = max(sol, bbpath[v]);
      value.push_back(under[v]);
    }

    ll total = 0;
    for (auto &i : edges) {
      total += graph_edges[i].cost;
    }

    ll cur = 0;
    for (int i = 1; i <= (int) edges.size(); i++) {
      cur += graph_edges[edges[i - 1]].cost;
      sum[i] = cur;
    }

    int y = (int) value.size();

    ll c1 = -INF, c2 = -INF;


    for (int r = 0; r < y; r++) {

      ll b1 = c1 + sum[r] + value[r];
      ll b2 = c2 + total + value[r] - sum[r];
      c1 = max(c1, value[r] - sum[r]);
      c2 = max(c2, sum[r] + value[r]);
      sol = max(sol, b1);
      sol = max(sol, b2);
    }
  }
  return sol;
}

signed main() {
  /// L < P

  ios::sync_with_stdio(0); cin.tie(0);

 /// freopen ("input2", "r", stdin);

  cin >> n;
  for (int i = 1; i <= n; i++) {
    int j, c;
    cin >> j >> c;
    graph_edges[i].a = i;
    graph_edges[i].b = j;
    graph_edges[i].cost = c;
  }
  for (int i = 1; i <= n; i++) {
    g[graph_edges[i].a].push_back(i);
    g[graph_edges[i].b].push_back(i);
  }

  ll sol = 0;

  for (int i = 1; i <= n; i++) {
    if (!vis[i]) {
      sol += solveComponent(i);
    }
  }

  cout << sol << "\n";

  return 0;
}

Compilation message

islands.cpp: In function 'll solveComponent(int)':
islands.cpp:111:9: warning: unused variable 'cost' [-Wunused-variable]
  111 |     int cost = graph_edges[index].cost;
      |         ^~~~

Subtask #1
33.0 / 33.0

# Verdict Execution time Memory Grader output
1 Correct 19 ms 39372 KB Output is correct
2 Correct 22 ms 39460 KB Output is correct
3 Correct 19 ms 39564 KB Output is correct
4 Correct 19 ms 39404 KB Output is correct
5 Correct 19 ms 39500 KB Output is correct
6 Correct 19 ms 39456 KB Output is correct
7 Correct 17 ms 39408 KB Output is correct
8 Correct 18 ms 39412 KB Output is correct
9 Correct 18 ms 39492 KB Output is correct
10 Correct 18 ms 39400 KB Output is correct
11 Correct 20 ms 39428 KB Output is correct

Subtask #2
3.0 / 3.0

# Verdict Execution time Memory Grader output
1 Correct 23 ms 39588 KB Output is correct
2 Correct 21 ms 39536 KB Output is correct

Subtask #3
4.0 / 4.0

# Verdict Execution time Memory Grader output
1 Correct 19 ms 39628 KB Output is correct
2 Correct 21 ms 39884 KB Output is correct

Subtask #4
10.0 / 10.0

# Verdict Execution time Memory Grader output
1 Correct 24 ms 40652 KB Output is correct
2 Correct 32 ms 43432 KB Output is correct
3 Correct 28 ms 40996 KB Output is correct
4 Correct 23 ms 40260 KB Output is correct

Subtask #5
10.0 / 10.0

# Verdict Execution time Memory Grader output
1 Correct 49 ms 44796 KB Output is correct
2 Correct 48 ms 47244 KB Output is correct

Subtask #6
10.0 / 10.0

# Verdict Execution time Memory Grader output
1 Correct 88 ms 54928 KB Output is correct
2 Correct 93 ms 60352 KB Output is correct
3 Correct 119 ms 70980 KB Output is correct

Subtask #7
10.0 / 10.0

# Verdict Execution time Memory Grader output
1 Correct 134 ms 64172 KB Output is correct
2 Correct 173 ms 94168 KB Output is correct
3 Correct 216 ms 97480 KB Output is correct
4 Correct 241 ms 124292 KB Output is correct

Subtask #8
0 / 10.0

# Verdict Execution time Memory Grader output
1 Correct 271 ms 91444 KB Output is correct
2 Runtime error 596 ms 131076 KB Execution killed with signal 9
3 Halted 0 ms 0 KB -

Subtask #9
0 / 10.0

# Verdict Execution time Memory Grader output
1 Runtime error 295 ms 131072 KB Execution killed with signal 9
2 Halted 0 ms 0 KB -