Submission #201629

#	Time	Username	Problem	Language	Result	Execution time	Memory
201629		waynetuinfor	Collecting Stamps 3 (JOI20_ho_t3)	C++17	100 / 100	144 ms	66808 KiB

ho_t3

#include <algorithm>
#include <array>
#include <iostream>
#include <vector>

int main() {
  int n, l;
  std::cin >> n >> l;
  std::vector<int> x(n + 2, 0), t(n + 2, 0);
  for (int i = 1; i <= n; ++i) std::cin >> x[i];
  for (int i = 1; i <= n; ++i) std::cin >> t[i];
  x[n + 1] = l;
  std::vector<std::vector<std::vector<std::array<int, 2>>>> dp(
      n + 2, std::vector<std::vector<std::array<int, 2>>>(
                 n + 2, std::vector<std::array<int, 2>>(n + 2)));
  constexpr int kInf = 1'000'000'000;
  for (int i = 0; i <= n + 1; ++i) {
    for (int j = 0; j <= n + 1; ++j) {
      for (int k = 0; k <= n + 1; ++k) {
        dp[i][j][k][0] = kInf;
        dp[i][j][k][1] = kInf;
      }
    }
  }
  dp[0][n + 1][0][0] = 0;
  dp[0][n + 1][0][1] = 0;
  for (int i = 0; i <= n + 1; ++i) {
    for (int j = n + 1; j >= 0; --j) {
      for (int k = 0; k <= n + 1; ++k) {
        if (dp[i][j][k][0] != kInf) {
          if (i + 1 < j) {
            int g = dp[i][j][k][0] + x[i + 1] - x[i];
            if (g <= t[i + 1] && k <= n) {
              dp[i + 1][j][k + 1][0] = std::min(dp[i + 1][j][k + 1][0], g);
            }
            dp[i + 1][j][k][0] = std::min(dp[i + 1][j][k][0], g);
          }
          if (j - 1 > i) {
            int g = dp[i][j][k][0] + l - (x[j - 1] - x[i]);
            if (g <= t[j - 1] && k <= n) {
              dp[i][j - 1][k + 1][1] = std::min(dp[i][j - 1][k + 1][1], g);
            }
            dp[i][j - 1][k][1] = std::min(dp[i][j - 1][k][1], g);
          }
        }
        if (dp[i][j][k][1] != kInf) {
          if (i + 1 < j) {
            int g = dp[i][j][k][1] + l - (x[j] - x[i + 1]);
            if (g <= t[i + 1] && k <= n) {
              dp[i + 1][j][k + 1][0] = std::min(dp[i + 1][j][k + 1][0], g);
            }
            dp[i + 1][j][k][0] = std::min(dp[i + 1][j][k][0], g);
          }
          if (j - 1 > i) {
            int g = dp[i][j][k][1] + x[j] - x[j - 1];
            if (g <= t[j - 1] && k <= n) {
              dp[i][j - 1][k + 1][1] = std::min(dp[i][j - 1][k + 1][1], g);
            }
            dp[i][j - 1][k][1] = std::min(dp[i][j - 1][k][1], g);
          }
        }
      }
    }
  }
  int ans = 0;
  for (int i = 0; i <= n + 1; ++i) {
    for (int j = 0; j <= n + 1; ++j) {
      for (int k = 0; k <= n + 1; ++k) {
        if (dp[i][j][k][0] != kInf) ans = std::max(ans, k);
        if (dp[i][j][k][1] != kInf) ans = std::max(ans, k);
      }
    }
  }
  std::cout << ans << "\n";
  return 0;
}

• Subtask 1: 5 / 5
• Subtask 2: 10 / 10
• Subtask 3: 10 / 10
• Subtask 4: 75 / 75