Submission #404588

# Submission time Handle Problem Language Result Execution time Memory
404588 2021-05-14T17:11:17 Z rama_pang Bomb (IZhO17_bomb) C++17
90 / 100
447 ms 74044 KB
#include <bits/stdc++.h>
using namespace std;

int N, M;
int A[2505][2505];
int up[2505][2505];
int dn[2505][2505];

int main() {
  ios::sync_with_stdio(0);
  cin.tie(0);

  cin >> N >> M;

  for (int i = 1; i <= N; i++) {
    for (int j = 1; j <= M; j++) {
      char c;
      cin >> c;
      A[i][j] = c - '0';
    }
  }

  // Solution:
  //
  // The upper bound on height and width is the minimum length
  // vertical and horizontal strip. Now, for a fixed width Y,
  // we want to determine the maximum height X. Note that,
  // if we have width Y, then for every maximal horizontal
  // strip, height is bounded by the minimum (top - bottom)
  // of the prefix and suffix of size Y.
  //
  // We only need to consider the prefix and suffix. Why?
  // For, after a prefix of size Y, let's move it to the right.
  // If the (top - bottom) decreased, that means that there is
  // a vertical strip which is shifted downwards, which means
  // it will occcupy a maximal horizontal strip -> we will compute
  // it later.
  //
  // Time complexity: O(N M).

  for (int j = 1; j <= M; j++) {
    for (int i = 1; i <= N; i++) {
      if (A[i][j]) {
        up[i][j] = 1 + up[i - 1][j];
      }
    }
    for (int i = N; i >= 1; i--) {
      if (A[i][j]) {
        dn[i][j] = 1 + dn[i + 1][j];
      }
    }
  }

  vector<int> ans(M + 2, N);
  for (int rep = 0; rep < 2; rep++) { // for prefix, then suffix
    for (int i = 1; i <= N; i++) {
      for (int j = 1; j <= M; j++) if (A[i][j] && !A[i][j - 1]) {
        int jj = j;
        while (jj + 1 <= M && A[i][jj + 1]) jj += 1;

        int len = jj - j + 1;
        int minUp = N;
        int minDn = N;
        for (int k = 1; k <= len; k++) {
          minUp = min(minUp, up[i][j + k - 1]);
          minDn = min(minDn, dn[i][j + k - 1]);
          ans[k] = min(ans[k], minUp + minDn - 1);
        }

        ans[len + 1] = 0;
        j = jj;
      }
    }
    for (int i = 1; i <= N; i++) {
      for (int j = 1; j + j <= M; j++) {
        swap(A[i][j], A[i][M - j + 1]);
        swap(up[i][j], up[i][M - j + 1]);
        swap(dn[i][j], dn[i][M - j + 1]);
      }
    }
  }

  int answer = 0;
  for (int i = 1; i <= M; i++) {
    ans[i] = min(ans[i], ans[i - 1]);
    answer = max(answer, i * ans[i]);
  }

  cout << answer << '\n';
  return 0;
}
# Verdict Execution time Memory Grader output
1 Correct 1 ms 332 KB Output is correct
2 Correct 1 ms 460 KB Output is correct
3 Correct 13 ms 30340 KB Output is correct
4 Correct 14 ms 30316 KB Output is correct
5 Correct 1 ms 332 KB Output is correct
6 Correct 1 ms 332 KB Output is correct
7 Incorrect 1 ms 332 KB Output isn't correct
8 Correct 1 ms 460 KB Output is correct
9 Correct 1 ms 460 KB Output is correct
10 Correct 1 ms 460 KB Output is correct
11 Correct 1 ms 460 KB Output is correct
12 Correct 1 ms 460 KB Output is correct
13 Correct 1 ms 460 KB Output is correct
14 Correct 1 ms 460 KB Output is correct
15 Correct 1 ms 460 KB Output is correct
16 Correct 1 ms 460 KB Output is correct
17 Correct 1 ms 1100 KB Output is correct
18 Correct 2 ms 1228 KB Output is correct
19 Correct 2 ms 1484 KB Output is correct
20 Correct 2 ms 1484 KB Output is correct
21 Correct 1 ms 972 KB Output is correct
22 Correct 1 ms 1228 KB Output is correct
23 Correct 2 ms 1612 KB Output is correct
24 Correct 1 ms 1356 KB Output is correct
25 Correct 2 ms 1612 KB Output is correct
26 Incorrect 2 ms 1612 KB Output isn't correct
27 Incorrect 5 ms 4748 KB Output isn't correct
28 Correct 6 ms 5068 KB Output is correct
29 Correct 7 ms 6476 KB Output is correct
30 Correct 11 ms 7628 KB Output is correct
31 Correct 8 ms 6092 KB Output is correct
32 Correct 8 ms 6988 KB Output is correct
33 Correct 10 ms 8012 KB Output is correct
34 Correct 5 ms 5580 KB Output is correct
35 Correct 10 ms 8136 KB Output is correct
36 Incorrect 11 ms 8140 KB Output isn't correct
37 Correct 1 ms 460 KB Output is correct
38 Correct 419 ms 73816 KB Output is correct
39 Correct 1 ms 460 KB Output is correct
40 Correct 54 ms 19980 KB Output is correct
41 Correct 1 ms 460 KB Output is correct
42 Correct 2 ms 1612 KB Output is correct
43 Correct 361 ms 73824 KB Output is correct
44 Correct 10 ms 8012 KB Output is correct
45 Correct 348 ms 73808 KB Output is correct
46 Correct 346 ms 73828 KB Output is correct
47 Correct 363 ms 73820 KB Output is correct
48 Correct 336 ms 73800 KB Output is correct
49 Incorrect 424 ms 73952 KB Output isn't correct
50 Correct 341 ms 73800 KB Output is correct
51 Correct 336 ms 73748 KB Output is correct
52 Correct 339 ms 73812 KB Output is correct
53 Correct 339 ms 73752 KB Output is correct
54 Correct 304 ms 73856 KB Output is correct
55 Correct 291 ms 73784 KB Output is correct
56 Correct 435 ms 73924 KB Output is correct
57 Correct 316 ms 73812 KB Output is correct
58 Correct 296 ms 73840 KB Output is correct
59 Correct 296 ms 73780 KB Output is correct
60 Incorrect 336 ms 73752 KB Output isn't correct
61 Incorrect 447 ms 74044 KB Output isn't correct
62 Incorrect 427 ms 73756 KB Output isn't correct
63 Incorrect 429 ms 73796 KB Output isn't correct
64 Incorrect 297 ms 73852 KB Output isn't correct
65 Correct 354 ms 73844 KB Output is correct
66 Correct 340 ms 73808 KB Output is correct
67 Correct 355 ms 73796 KB Output is correct
68 Correct 380 ms 73812 KB Output is correct
69 Correct 294 ms 73736 KB Output is correct
70 Correct 173 ms 59128 KB Output is correct
71 Correct 266 ms 73784 KB Output is correct
72 Correct 307 ms 73844 KB Output is correct
73 Correct 292 ms 73828 KB Output is correct
74 Correct 303 ms 73796 KB Output is correct
75 Correct 313 ms 73848 KB Output is correct
76 Correct 306 ms 73852 KB Output is correct
77 Correct 302 ms 73828 KB Output is correct
78 Correct 345 ms 73776 KB Output is correct
79 Correct 250 ms 73812 KB Output is correct
80 Correct 245 ms 73804 KB Output is correct
81 Correct 253 ms 73832 KB Output is correct
82 Correct 324 ms 73860 KB Output is correct
83 Correct 297 ms 73824 KB Output is correct
84 Correct 247 ms 73896 KB Output is correct
85 Correct 297 ms 73760 KB Output is correct
86 Correct 417 ms 73856 KB Output is correct
87 Correct 300 ms 73784 KB Output is correct
88 Correct 297 ms 73764 KB Output is correct
89 Correct 332 ms 73848 KB Output is correct
90 Correct 200 ms 59152 KB Output is correct
91 Correct 318 ms 73788 KB Output is correct
92 Correct 329 ms 73756 KB Output is correct
93 Correct 400 ms 73900 KB Output is correct
94 Correct 335 ms 73928 KB Output is correct
95 Correct 309 ms 73844 KB Output is correct
96 Correct 309 ms 73768 KB Output is correct
97 Correct 406 ms 73852 KB Output is correct
98 Correct 307 ms 73776 KB Output is correct
99 Correct 321 ms 73736 KB Output is correct
100 Correct 415 ms 73796 KB Output is correct