m)){m[used] = true;return true;}}}m[used] = false;return fa

class Solution { public: bool canIWin(int maxChoosableInteger, int desiredTotal) { if (maxChoosableInteger >= desiredTotal) { return true; } if (maxChoosableInteger * (maxChoosableInteger + 1) / 2 < desiredTotal) { return false; } unordered_map<int, bool> m; return canWin(maxChoosableInteger, desiredTotal, 0, m); } bool canWin(int length, int total, int used, unordered_map<int, bool>& m) { if (m.count(used)) { return m[used]; } for (int i = 0; i < length; ++i) { int cur = (1 << i); if ((cur & used) == 0) { if (total <= i + 1 || !canWin(length, total - (i + 1), cur | used, m)) { m[used] = true; return true; } } } m[used] = false; return false; } };

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