add: 220122

2201/220122.cpp

@@ -0,0 +1,76 @@
+#include <cstdio>
+#include <cstdint>
+
+// Clang does not accept this constexpr Solver, but MSVC does.
+template<int N>
+struct Solver {
+	int bobs[3000];
+	int endPosition;
+	constexpr Solver() : bobs() {
+		int dp[N + 5][2]{{-1, 1}};
+		auto f = [&dp](int n, int who, auto&& fr) {
+			if (dp[n][who])
+				return dp[n][who];
+			for (int i = 1; i * i <= n; ++i) {
+				if (fr(n - i * i, who ^ 1, fr) == (who ? -1 : 1))
+					return dp[n][who] = (who ? -1 : 1);
+			}
+			return dp[n][who] = (who ? 1 : -1);
+		};
+		int pos = 0;
+		for (int i = 0; i < N + 3; ++i) {
+			if (f(i, 0, f) == -1){
+				bobs[pos++] = i;
+			}
+		}
+		endPosition = pos;
+	}
+};
+
+/**
+ * 1510. Stone Game IV
+ * Alice and Bob take turns playing a game, with Alice starting first.
+ * Initially, there are n stones in a pile. On each player's turn, that player makes a move consisting of removing any non-zero square number of stones in the pile.
+ * Also, if a player cannot make a move, he/she loses the game.
+ * Given a positive integer n, return true if and only if Alice wins the game otherwise return false, assuming both players play optimally.
+ */
+
+class Solution {
+private:
+	static constexpr Solver<100005> answer;
+public:
+	static bool winnerSquareGame(int n) {
+		for (int i = 0; i < answer.endPosition; ++i) {
+			if (answer.bobs[i] == n) {
+				return false;
+			}
+		}
+		return true;
+	}
+};
+
+class SolutionOld {
+private:
+	// 0 -> Unknown, 1 -> Alice, -1 -> Bob
+	// dp[n][0] -> Alice to take, [1] -> Bob to take;
+	int8_t dp[100005][2]{{-1, 1}};
+	int8_t d(int n, int8_t who) {
+		if (dp[n][who])
+			return dp[n][who];
+		for (int i = 1; i * i <= n; ++i) {
+			if (d(n - i * i, who ^ 1) == (who ? -1 : 1))
+				return dp[n][who] = (who ? -1 : 1);
+		}
+		return dp[n][who] = (who ? 1 : -1);
+	}
+public:
+	bool winnerSquareGame(int n) {
+		return d(n, 0) == 1;
+	}
+};
+
+int main() {
+	SolutionOld solver;
+	std::printf("%s\n", Solution::winnerSquareGame(4) ? "true" : "false");
+	return 0;
+}

2201/CMakeLists.txt

@@ -3,4 +3,4 @@ PROJECT(2201)
 
 SET(CMAKE_CXX_STANDARD 23)
 
-ADD_EXECUTABLE(2201 220122-CN.cpp)
+ADD_EXECUTABLE(2201 220122.cpp)