108 lines
2.2 KiB
C++
108 lines
2.2 KiB
C++
#include <bits/stdc++.h> // {{{
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// https://codeforces.com/blog/entry/96344
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#pragma GCC optimize("O2,unroll-loops")
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#pragma GCC target("avx2,bmi,bmi2,lzcnt,popcnt")
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using namespace std;
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template <typename T>
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constexpr T MIN = std::numeric_limits<T>::min();
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template <typename T>
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constexpr T MAX = std::numeric_limits<T>::max();
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template <typename T>
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[[nodiscard]] static T sc(auto&& x) {
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return static_cast<T>(x);
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}
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template <typename T>
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[[nodiscard]] static T sz(auto&& x) {
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return static_cast<T>(x.size());
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}
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using ll = long long;
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using ld = long double;
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template <typename T>
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using vec = std::vector<T>;
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template <typename T, size_t N>
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using arr = std::array<T, N>;
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#define ff first
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#define ss second
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#define eb emplace_back
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#define pb push_back
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#define all(x) (x).begin(), (x).end()
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#define rall(x) (x).rbegin(), (x).rend()
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// }}}
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bitset<7 * 7 + 1> seen;
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vec<pair<int, int>> dirs;
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unordered_map<char, pair<int, int>> dir_map{
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{'U', {-1, 0}}, {'D', {1, 0}}, {'L', {0, -1}}, {'R', {0, 1}}};
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ll ans = 0;
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string s;
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void dfs(int r, int c, int i) {
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if (min(r, c) < 0 || max(r, c) > 6 || seen[r * 7 + c]) {
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return;
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}
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if (r == 6 && c == 0) {
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ans += i == 48;
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return;
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}
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seen[r * 7 + c] = true;
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bool up = (r > 0 && !seen[(r - 1) * 7 + c]);
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bool down = (r < 6 && !seen[(r + 1) * 7 + c]);
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bool left = (c > 0 && !seen[r * 7 + (c - 1)]);
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bool right = (c < 6 && !seen[r * 7 + (c + 1)]);
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if ((up && down && !left && !right) || (!up && !down && left && right)) {
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seen[r * 7 + c] = false;
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return;
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}
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int open_count = up + down + left + right;
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if (open_count == 1) {
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if (up) dfs(r - 1, c, i + 1);
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else if (down) dfs(r + 1, c, i + 1);
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else if (left) dfs(r, c - 1, i + 1);
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else if (right) dfs(r, c + 1, i + 1);
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seen[r * 7 + c] = false;
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return;
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}
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if (s[i] == '?') {
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for (auto& [dr, dc] : dirs) {
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dfs(r + dr, c + dc, i + 1);
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}
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} else {
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dfs(r + dir_map[s[i]].ff, c + dir_map[s[i]].ss, i + 1);
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}
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seen[r * 7 + c] = false;
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}
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void solve() {
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dirs.eb(1, 0);
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dirs.eb(0, 1);
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dirs.eb(-1, 0);
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dirs.eb(0, -1);
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cin >> s;
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dfs(0, 0, 0);
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cout << ans << endl;
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}
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int main() { // {{{
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cin.tie(nullptr)->sync_with_stdio(false);
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solve();
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return 0;
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}
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// }}}
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