Add solution #488

Author: JoshCrozier

README.md

@@ -391,6 +391,7 @@
 483|[Smallest Good Base](./0483-smallest-good-base.js)|Hard|
 485|[Max Consecutive Ones](./0485-max-consecutive-ones.js)|Easy|
 486|[Predict the Winner](./0486-predict-the-winner.js)|Medium|
+488|[Zuma Game](./0488-zuma-game.js)|Hard|
 491|[Non-decreasing Subsequences](./0491-non-decreasing-subsequences.js)|Medium|
 492|[Construct the Rectangle](./0492-construct-the-rectangle.js)|Easy|
 496|[Next Greater Element I](./0496-next-greater-element-i.js)|Easy|

solutions/0488-zuma-game.js

@@ -0,0 +1,101 @@
+/**
+ * 488. Zuma Game
+ * https://leetcode.com/problems/zuma-game/
+ * Difficulty: Hard
+ *
+ * You are playing a variation of the game Zuma.
+ *
+ * In this variation of Zuma, there is a single row of colored balls on a board, where each ball
+ * can be colored red 'R', yellow 'Y', blue 'B', green 'G', or white 'W'. You also have several
+ * colored balls in your hand.
+ *
+ * Your goal is to clear all of the balls from the board. On each turn:
+ * - Pick any ball from your hand and insert it in between two balls in the row or on either end
+ *   of the row.
+ * - If there is a group of three or more consecutive balls of the same color, remove the group of
+ *   balls from the board.
+ *   - If this removal causes more groups of three or more of the same color to form, then continue
+ *     removing each group until there are none left.
+ * - If there are no more balls on the board, then you win the game.
+ * - Repeat this process until you either win or do not have any more balls in your hand.
+ *
+ * Given a string board, representing the row of balls on the board, and a string hand, representing
+ * the balls in your hand, return the minimum number of balls you have to insert to clear all the
+ * balls from the board. If you cannot clear all the balls from the board using the balls in your
+ * hand, return -1.
+ */
+
+/**
+ * @param {string} board
+ * @param {string} hand
+ * @return {number}
+ */
+var findMinStep = function(board, hand) {
+  const handCount = {};
+  for (const ball of hand) {
+    handCount[ball] = (handCount[ball] || 0) + 1;
+  }
+
+  const memo = new Map();
+
+  function dfs(board, hand) {
+    if (board.length === 0) return 0;
+    if (Object.values(hand).every(count => count === 0)) return -1;
+    const key = board + getHandString(hand);
+    if (memo.has(key)) return memo.get(key);
+    let minSteps = Infinity;
+
+    for (const color in hand) {
+      if (hand[color] <= 0) continue;
+      hand[color]--;
+      for (let i = 0; i <= board.length; i++) {
+        if (i > 0 && i < board.length) {
+          const left = board[i-1];
+          const right = board[i];
+          if (left !== color && right !== color && left !== right) continue;
+        }
+        const newBoard = board.slice(0, i) + color + board.slice(i);
+        const afterRemove = removeConsecutive(newBoard);
+        const steps = dfs(afterRemove, hand);
+        if (steps !== -1) {
+          minSteps = Math.min(minSteps, steps + 1);
+        }
+      }
+      hand[color]++;
+    }
+    const result = minSteps === Infinity ? -1 : minSteps;
+    memo.set(key, result);
+    return result;
+  };
+
+  return dfs(board, handCount);
+};
+
+function getHandString(hand) {
+  return Object.entries(hand)
+    .filter(([_, count]) => count > 0)
+    .sort(([a], [b]) => a.localeCompare(b))
+    .map(([color, count]) => color + count)
+    .join('');
+}
+
+function removeConsecutive(board) {
+  let changed = true;
+  while (changed) {
+    changed = false;
+    for (let i = 0; i < board.length;) {
+      let j = i;
+      while (j < board.length && board[j] === board[i]) {
+        j++;
+      }
+      if (j - i >= 3) {
+        board = board.substring(0, i) + board.substring(j);
+        changed = true;
+        i = 0;
+      } else {
+        i++;
+      }
+    }
+  }
+  return board;
+}