Submission #964432

#	Time	Username	Problem	Language	Result	Execution time	Memory
964432		nguyentunglam	Soccer Stadium (IOI23_soccer)	C++17	100 / 100	4473 ms	690368 KiB

soccer

#include "soccer.h"
#include<bits/stdc++.h>
#define all(v) v.begin(), v.end()
using namespace std;

const int N = 2010;

int n;

bool a[N][N];

vector<int> arr[N];

int check_valid() {
  for(int col = 0; col < n; col++) {
    for(int row = 0; row < n; row++) if (a[row][col] == 0) arr[col].push_back(row);
  }

  int st = 0;
  while (st < n && arr[st].empty()) st++;
  if (st == n) return 0;
  int ed = st;

  while (ed < n && !arr[ed].empty()) ed++; ed--;
  for(int i = 1; i < st; i++) if (!arr[i].empty()) return 0;
  for(int i = ed + 1; i < n; i++) if (!arr[i].empty()) return 0;
  for(int i = st; i <= ed; i++) if (arr[i].size() != arr[i].back() - arr[i][0] + 1) return 0;

  int cnt = 0;

  for(int i = st; i <= ed; i++) cnt += arr[i].size();

  int L = max(arr[st][0], arr[ed][0]);
  int R = min(arr[st].back(), arr[ed].back());
  while (st <= ed) {
    if (arr[st].size() <= arr[ed].size()) {
      if (arr[st][0] <= L && arr[st].back() >= R) {
        L = arr[st][0];
        R = arr[st].back();
        st++;
      }
      else return 0;
    }
    else {
      if (arr[ed][0] <= L && arr[ed].back() >= R) {
        L = arr[ed][0];
        R = arr[ed].back();
        ed--;
      }
      else return 0;
    }
  }
  return cnt;
}

namespace sub4 {
const int N = 51;
int pref[N][N];
int dp[N][N][N][N];
int solve() {
  for(int i = 0; i < n; i++) {
    pref[i][0] = a[i][0];
    for(int j = 1; j < n; j++) pref[i][j] = pref[i][j - 1] + a[i][j];
  }

  auto check = [&] (int i, int l, int r) {
    int sum = pref[i][r];
    if (l > 0) sum -= pref[i][l - 1];
    return sum == 0;
  };

  int ans = 0;

//  cout << check(1, 1, 2) << endl;

  memset(dp, -61, sizeof(dp));
  for(int i = 0; i < n; i++) {
    for(int u = 0; u < n; u++) for(int v = u; v < n; v++) if (check(i, u, v)) dp[i][i][u][v] = v - u + 1;
  }

  for(int x = n - 1; x >= 0; x--) for(int y = x; y <= n; y++) {
    for(int u = 0; u < n; u++) for(int v = u; v < n; v++) {
      for(int _u = 0; _u <= u; _u++) for(int _v = v; _v < n; _v++) {
        if (y + 1 < n && check(y + 1, u, v)) dp[x][y + 1][u][v] = max(dp[x][y + 1][u][v], dp[x][y][_u][_v] + v - u + 1);
        if (x > 0 && check(x - 1, u, v)) dp[x - 1][y][u][v] = max(dp[x - 1][y][u][v], dp[x][y][_u][_v] + v - u + 1);
      }
      ans = max(ans, dp[x][y][u][v]);
    }
  }

  return ans;
}
}

namespace AC {
const int N = 2010, M = 2e3 * 2e3 * 2 + 10;

int b[N], L[N], R[N], dp[M], trans[2][M];

int close[2][N][N];

vector<int> open[2][N][N], lst[N];

tuple<int, int, int, int> rect[M];

int solve() {

//  for(int i = 1; i <= n; i++) {
//    for(int j = 1; j <= n; j++) cout << a[i][j] << " "; cout << endl;
//  }
  int m = 0;

  auto histogram = [&] () {
    stack<int> st;
    for(int i = 1; i <= n; i++) {
      while (!st.empty() && b[st.top()] >= b[i]) st.pop();
      L[i] = st.empty() ? 0 : st.top();
      st.push(i);
    }
    while (!st.empty()) st.pop();
    for(int i = n; i >= 1; i--) {
      while (!st.empty() && b[st.top()] >= b[i]) st.pop();
      R[i] = st.empty() ? n + 1 : st.top();
      st.push(i);
    }
  };

  for(int i = 1; i <= n; i++) {
    for(int j = 1; j <= n; j++) {
      if (a[i][j]) b[j] = 0;
      else b[j]++;
    }
    histogram();
    for(int j = 1; j <= n; j++) if (b[j]) {
      rect[++m] = make_tuple(i - b[j] + 1, i, L[j] + 1, R[j] - 1);
    }
  }

  for(int j = 1; j <= n; j++) b[j] = 0;

  for(int i = n; i >= 1; i--) {
    for(int j = 1; j <= n; j++) {
      if (a[i][j]) b[j] = 0;
      else b[j]++;
    }
    histogram();
    for(int j = 1; j <= n; j++) if (b[j]) {
      rect[++m] = make_tuple(i, i + b[j] - 1, L[j] + 1, R[j] - 1);
    }
  }

  for(int i = 1; i <= m; i++) {
    lst[get<1> (rect[i]) - get<0> (rect[i])].push_back(i);
  }

  for(int delta = 0; delta < n; delta++) {
    for(int &i : lst[delta]) {
      int x1, x2, y1, y2; tie(x1, x2, y1, y2) = rect[i];
      open[0][x2][y1].emplace_back(i);
      close[0][x2][y2]++;
      open[1][x1][y1].emplace_back(i);
      close[1][x1][y2]++;
    }
  }

  for(int i = 1; i <= n; i++) for(int t = 0; t < 2; t++) {
    stack<int> st;
    for(int j = 1; j <= n; j++) {
      for(auto &k : open[t][i][j]) {
        trans[t][k] = st.empty() ? 0 : st.top();
        st.push(k);
      }
      while (close[t][i][j]--) st.pop();
    }
  }

  int ans = 0;

  for(int delta = 0; delta < n; delta++) {
    for(int &i : lst[delta]) {
      int x1, x2, y1, y2; tie(x1, x2, y1, y2) = rect[i];
      dp[i] = (x2 - x1 + 1) * (y2 - y1 + 1);
      if (trans[0][i]) { // top
        int j = trans[0][i];
        dp[i] = max(dp[i], dp[j] + (get<0> (rect[j]) - x1) * (y2 - y1 + 1));
      } // bottom
      if (trans[1][i]) {
        int j = trans[1][i];
        dp[i] = max(dp[i], dp[j] + (x2 - get<1> (rect[j])) * (y2 - y1 + 1));
      }
      ans = max(ans, dp[i]);
    }
  }
  cerr << 1.0 * clock() / CLOCKS_PER_SEC << endl;

  return ans;
}
}


int biggest_stadium(int N, std::vector<std::vector<int>> F)
{
  n = N;
  for(int i = 0; i < n; i++) for(int j = 0; j < n; j++) a[i][j] = F[i][j];
//  if (n <= 30) return sub4::solve();
//  if (n <= 500) return sub5::solve();
  for(int i = 1; i <= n; i++) for(int j = 1; j <= n; j++) a[i][j] = F[i - 1][j - 1];
  return AC::solve();
}

#ifdef ngu
int main()
{
  freopen ("task.inp", "r", stdin);
  freopen ("task.out", "w", stdout);
    int N;
    assert(1 == scanf("%d", &N));
    std::vector<std::vector<int>> F(N, std::vector<int>(N));
    for (int i = 0; i < N; i++)
    {
        for (int j = 0; j < N; j++)
        {
            assert(1 == scanf("%d", &F[i][j]));
        }
    }
    fclose(stdin);

    int res = biggest_stadium(N, F);

    printf("%d\n", res);
    fclose(stdout);
    return 0;
}
#endif // ngu

Compilation message (stderr)

soccer.cpp: In function 'int check_valid()':
soccer.cpp:24:3: warning: this 'while' clause does not guard... [-Wmisleading-indentation]
   24 |   while (ed < n && !arr[ed].empty()) ed++; ed--;
      |   ^~~~~
soccer.cpp:24:44: note: ...this statement, but the latter is misleadingly indented as if it were guarded by the 'while'
   24 |   while (ed < n && !arr[ed].empty()) ed++; ed--;
      |                                            ^~
soccer.cpp:27:51: warning: comparison of integer expressions of different signedness: 'std::vector<int>::size_type' {aka 'long unsigned int'} and '__gnu_cxx::__alloc_traits<std::allocator<int>, int>::value_type' {aka 'int'} [-Wsign-compare]
   27 |   for(int i = st; i <= ed; i++) if (arr[i].size() != arr[i].back() - arr[i][0] + 1) return 0;
      |                                     ~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 0: 0 / 0
• Subtask 1: 6 / 6
• Subtask 2: 8 / 8
• Subtask 3: 22 / 22
• Subtask 4: 18 / 18
• Subtask 5: 16 / 16
• Subtask 6: 30 / 30