project-euler-solutions/0011.cc at main · deantee/project-euler-solutions · GitHub

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#include <bits/stdc++.h>

using namespace std;
using ll = long long;

int main() {
  ios::sync_with_stdio(false);
  cin.tie(nullptr);
  int arr[][20] = {
      {8, 2, 22, 97, 38, 15, 0, 40, 0, 75, 4, 5, 7, 78, 52, 12, 50, 77, 91, 8},
      {49, 49, 99, 40, 17, 81, 18, 57, 60, 87,
       17, 40, 98, 43, 69, 48, 4,  56, 62, 0},
      {81, 49, 31, 73, 55, 79, 14, 29, 93, 71,
       40, 67, 53, 88, 30, 3,  49, 13, 36, 65},
      {52, 70, 95, 23, 4,  60, 11, 42, 69, 24,
       68, 56, 1,  32, 56, 71, 37, 2,  36, 91},
      {22, 31, 16, 71, 51, 67, 63, 89, 41, 92,
       36, 54, 22, 40, 40, 28, 66, 33, 13, 80},
      {24, 47, 32, 60, 99, 3,  45, 2,  44, 75,
       33, 53, 78, 36, 84, 20, 35, 17, 12, 50},
      {32, 98, 81, 28, 64, 23, 67, 10, 26, 38,
       40, 67, 59, 54, 70, 66, 18, 38, 64, 70},
      {67, 26, 20, 68, 2,  62, 12, 20, 95, 63,
       94, 39, 63, 8,  40, 91, 66, 49, 94, 21},
      {24, 55, 58, 5,  66, 73, 99, 26, 97, 17,
       78, 78, 96, 83, 14, 88, 34, 89, 63, 72},
      {21, 36, 23, 9,  75, 0,  76, 44, 20, 45,
       35, 14, 0,  61, 33, 97, 34, 31, 33, 95},
      {78, 17, 53, 28, 22, 75, 31, 67, 15, 94,
       3,  80, 4,  62, 16, 14, 9,  53, 56, 92},
      {16, 39, 5, 42, 96, 35, 31, 47, 55, 58,
       88, 24, 0, 17, 54, 24, 36, 29, 85, 57},
      {86, 56, 0,  48, 35, 71, 89, 7,  5,  44,
       44, 37, 44, 60, 21, 58, 51, 54, 17, 58},
      {19, 80, 81, 68, 5,  94, 47, 69, 28, 73,
       92, 13, 86, 52, 17, 77, 4,  89, 55, 40},
      {4,  52, 8,  83, 97, 35, 99, 16, 7,  97,
       57, 32, 16, 26, 26, 79, 33, 27, 98, 66},
      {88, 36, 68, 87, 57, 62, 20, 72, 3,  46,
       33, 67, 46, 55, 12, 32, 63, 93, 53, 69},
      {4,  42, 16, 73, 38, 25, 39, 11, 24, 94,
       72, 18, 8,  46, 29, 32, 40, 62, 76, 36},
      {20, 69, 36, 41, 72, 30, 23, 88, 34, 62,
       99, 69, 82, 67, 59, 85, 74, 4,  36, 16},
      {20, 73, 35, 29, 78, 31, 90, 1,  74, 31,
       49, 71, 48, 86, 81, 16, 23, 57, 5,  54},
      {1,  70, 54, 71, 83, 51, 54, 69, 16, 92,
       33, 48, 61, 43, 52, 1,  89, 19, 67, 48}};
  ll ans{LLONG_MIN};
  auto dfs = [&](auto&& self, ll x, ll y, ll dx, ll dy, ll i, ll p) -> ll {
    if (i == 4) {
      return p;
    }
    if (x < 0 || y < 0 || x >= 20 || y >= 20) {
      return LLONG_MIN;
    }
    if (arr[x][y] == 0) {
      return 0;
    }
    return self(self, x + dx, y + dy, dx, dy, i + 1, p * arr[x][y]);
  };
  for (ll i = 0; i < 20; ++i) {
    for (ll j = 0; j < 20; ++j) {
      ans = max(ans, dfs(dfs, i, j, -1, 1, 0, 1));
      ans = max(ans, dfs(dfs, i, j, 0, 1, 0, 1));
      ans = max(ans, dfs(dfs, i, j, 1, 0, 0, 1));
      ans = max(ans, dfs(dfs, i, j, 1, 1, 0, 1));
    }
  }
  cout << ans << '\n';
}