Add twofive.cpp

01/twofive.cpp

@@ -0,0 +1,73 @@
+#include <bits/stdc++.h>
+#define f first
+#define s second
+using namespace std;
+using ll = long long;
+using ii = pair<int, int>;
+constexpr int MX = 5;
+
+char A[MX*MX];
+bitset<MX*MX> vis;
+map<vector<int>, int> dp;
+
+int f(vector<int> & v) {
+	for (int i = 1; i < MX; ++i) if (v[i-1] < v[i]) return 0;
+	for (int i = 0; i < MX; ++i) if (v[i] > MX) return 0;
+	
+	int sum = 0;
+	for (int i = 0; i < MX; ++i) sum += v[i];
+	if (sum == MX*MX) return 1;
+	
+	if (dp.find(v) != dp.end()) return dp[v];
+
+	int ret = 0;
+	for (int i = 0; i < MX; ++i)
+		if (A[i*MX+v[i]] == 'A'+sum || !A[i*MX+v[i]])
+			++v[i], ret += f(v), --v[i];
+	return dp[v] = ret;
+}
+
+string getk(int k) {
+	string ret(MX*MX, '0');
+
+	vis.reset();
+	memset(A, 0, sizeof A);
+	for (int i = 0; i < MX*MX; ++i) {
+		for (int j = 0; j < MX*MX; ++j) {
+			if (vis[j]) continue;
+			vis[j] = 1;
+			
+			A[i] = 'A'+j;
+			dp.clear();
+			vector<int> v(MX, 0);
+			int tmp = f(v);
+			
+			if (tmp >= k) break;
+			k -= tmp;
+			vis[j] = 0;
+		}
+		ret[i] = A[i];
+	}
+	return ret;
+}
+
+int main() {
+	if (fopen("in", "r")) freopen("in", "r", stdin), freopen("out", "w", stdout);
+	ios_base::sync_with_stdio(0), cin.tie(0);
+
+	char c; cin >> c;
+	if (c == 'N') {
+		int M; cin >> M;
+		cout << getk(M);
+	}
+	else {
+		string S; cin >> S;
+		int l = 0, h = 1e9;
+		while (l < h) {
+			int m = (l+h)/2;
+			string tmp = getk(m);
+			tmp < S ? l = m+1 : h = m;
+		}
+		cout << l;
+	}
+}