464. Can I Win

Author: amitbansal7

can-i-win.cpp

@@ -0,0 +1,60 @@
+//Runtime: 183 ms
+class Solution {
+public:
+	unordered_map<int, bool> Mp;
+	vector<bool>used;
+	int findkey(vector<bool>&used)
+	{
+		int num = 0;
+		for (bool a : used)
+		{
+			num <<= 1;
+			if (a) num |= 1;
+
+		}
+		return num;
+	}
+
+	bool solve(int dt)
+	{
+		if (dt <= 0)
+			return 0;
+
+		int key = findkey(used);
+
+		auto it = Mp.find(key);
+		if (it != Mp.end())
+			return it->second;
+
+		for (int i = 1; i < used.size(); i++)
+		{
+			if (!used[i])
+			{
+				used[i] = 1;
+
+				if (!solve(dt - i))
+				{
+					Mp[key] = 1;
+					used[i] = 0;
+					return 1;
+				}
+				used[i] = 0;
+			}
+		}
+		Mp[key] = 0;
+		return 0;
+	}
+
+	bool canIWin(int maxChoosableInteger, int desiredTotal) {
+		if (desiredTotal <= 0)
+			return 1;
+		int sum = (1 + maxChoosableInteger) * maxChoosableInteger / 2;
+		if (sum < desiredTotal)
+			return 0;
+
+		for (int i = 0; i <= maxChoosableInteger; i++)
+			used.push_back(0);
+
+		return solve(desiredTotal);
+	}
+};