Add solution #464

Author: JoshCrozier

README.md

@@ -372,6 +372,7 @@
 461|[Hamming Distance](./0461-hamming-distance.js)|Easy|
 462|[Minimum Moves to Equal Array Elements II](./0462-minimum-moves-to-equal-array-elements-ii.js)|Medium|
 463|[Island Perimeter](./0463-island-perimeter.js)|Medium|
+464|[Can I Win](./0464-can-i-win.js)|Medium|
 472|[Concatenated Words](./0472-concatenated-words.js)|Hard|
 476|[Number Complement](./0476-number-complement.js)|Easy|
 482|[License Key Formatting](./0482-license-key-formatting.js)|Easy|

solutions/0464-can-i-win.js

@@ -0,0 +1,49 @@
+/**
+ * 464. Can I Win
+ * https://leetcode.com/problems/can-i-win/
+ * Difficulty: Medium
+ *
+ * In the "100 game" two players take turns adding, to a running total, any integer from 1 to 10.
+ * The player who first causes the running total to reach or exceed 100 wins.
+ *
+ * What if we change the game so that players cannot re-use integers?
+ *
+ * For example, two players might take turns drawing from a common pool of numbers from 1 to 15
+ * without replacement until they reach a total >= 100.
+ *
+ * Given two integers maxChoosableInteger and desiredTotal, return true if the first player to
+ * move can force a win, otherwise, return false. Assume both players play optimally.
+ */
+
+/**
+ * @param {number} maxChoosableInteger
+ * @param {number} desiredTotal
+ * @return {boolean}
+ */
+var canIWin = function(maxChoosableInteger, desiredTotal) {
+  const memo = new Map();
+  const sum = (maxChoosableInteger * (maxChoosableInteger + 1)) / 2;
+
+  if (desiredTotal <= 0) return true;
+  if (sum < desiredTotal) return false;
+
+  return check(0, desiredTotal);
+
+  function check(state, remaining) {
+    if (remaining <= 0) return false;
+
+    const key = state.toString();
+    if (memo.has(key)) return memo.get(key);
+
+    for (let i = 1; i <= maxChoosableInteger; i++) {
+      const mask = 1 << i;
+      if (!(state & mask) && (i >= remaining || !check(state | mask, remaining - i))) {
+        memo.set(key, true);
+        return true;
+      }
+    }
+
+    memo.set(key, false);
+    return false;
+  }
+};