Add solution #294

Author: JoshCrozier

README.md

@@ -282,6 +282,7 @@
 291|[Word Pattern II](./solutions/0291-word-pattern-ii.js)|Medium|
 292|[Nim Game](./solutions/0292-nim-game.js)|Easy|
 293|[Flip Game](./solutions/0293-flip-game.js)|Easy|
+294|[Flip Game II](./solutions/0294-flip-game-ii.js)|Medium|
 295|[Find Median from Data Stream](./solutions/0295-find-median-from-data-stream.js)|Hard|
 297|[Serialize and Deserialize Binary Tree](./solutions/0297-serialize-and-deserialize-binary-tree.js)|Hard|
 299|[Bulls and Cows](./solutions/0299-bulls-and-cows.js)|Medium|

solutions/0294-flip-game-ii.js

@@ -0,0 +1,40 @@
+/**
+ * 294. Flip Game II
+ * https://leetcode.com/problems/flip-game-ii/
+ * Difficulty: Medium
+ *
+ * You are playing a Flip Game with your friend.
+ *
+ * You are given a string currentState that contains only '+' and '-'. You and your friend take
+ * turns to flip two consecutive "++" into "--". The game ends when a person can no longer make
+ * a move, and therefore the other person will be the winner.
+ *
+ * Return true if the starting player can guarantee a win, and false otherwise.
+ */
+
+/**
+ * @param {string} currentState
+ * @return {boolean}
+ */
+var canWin = function(currentState) {
+  const map = new Map();
+
+  return canWinFrom(currentState);
+
+  function canWinFrom(state) {
+    if (map.has(state)) return map.get(state);
+
+    for (let i = 0; i < state.length - 1; i++) {
+      if (state[i] === '+' && state[i + 1] === '+') {
+        const nextState = state.slice(0, i) + '--' + state.slice(i + 2);
+        if (!canWinFrom(nextState)) {
+          map.set(state, true);
+          return true;
+        }
+      }
+    }
+
+    map.set(state, false);
+    return false;
+  }
+};