Add solution #691

Author: JoshCrozier

README.md

@@ -522,6 +522,7 @@
 688|[Knight Probability in Chessboard](./0688-knight-probability-in-chessboard.js)|Medium|
 689|[Maximum Sum of 3 Non-Overlapping Subarrays](./0689-maximum-sum-of-3-non-overlapping-subarrays.js)|Hard|
 690|[Employee Importance](./0690-employee-importance.js)|Medium|
+691|[Stickers to Spell Word](./0691-stickers-to-spell-word.js)|Hard|
 692|[Top K Frequent Words](./0692-top-k-frequent-words.js)|Medium|
 693|[Binary Number with Alternating Bits](./0693-binary-number-with-alternating-bits.js)|Easy|
 695|[Max Area of Island](./0695-max-area-of-island.js)|Medium|

solutions/0691-stickers-to-spell-word.js

@@ -0,0 +1,46 @@
+/**
+ * 691. Stickers to Spell Word
+ * https://leetcode.com/problems/stickers-to-spell-word/
+ * Difficulty: Hard
+ *
+ * We are given n different types of stickers. Each sticker has a lowercase English word on it.
+ *
+ * You would like to spell out the given string target by cutting individual letters from your
+ * collection of stickers and rearranging them. You can use each sticker more than once if you
+ * want, and you have infinite quantities of each sticker.
+ *
+ * Return the minimum number of stickers that you need to spell out target. If the task is
+ * impossible, return -1.
+ *
+ * Note: In all test cases, all words were chosen randomly from the 1000 most common US English
+ * words, and target was chosen as a concatenation of two random words.
+ */
+
+/**
+ * @param {string[]} stickers
+ * @param {string} target
+ * @return {number}
+ */
+var minStickers = function(stickers, target) {
+  const dp = new Map([['', 0]]);
+  return helper(target);
+
+  function helper(str) {
+    if (dp.has(str)) return dp.get(str);
+    let result = Infinity;
+
+    for (const s of stickers.filter(s => s.includes(str[0]))) {
+      result = Math.min(result, 1 + helper(calcDiff(str, s)));
+    }
+
+    dp.set(str, result === Infinity || result === 0 ? -1 : result);
+    return dp.get(str);
+  }
+
+  function calcDiff(str1, str2) {
+    for (const c of str2) {
+      if (str1.includes(c)) str1 = str1.replace(c, '');
+    }
+    return str1;
+  }
+};