Add solution #1531

Author: JoshCrozier

README.md

@@ -1,4 +1,4 @@
-# 1,350 LeetCode solutions in JavaScript
+# 1,351 LeetCode solutions in JavaScript
 
 [https://leetcodejavascript.com](https://leetcodejavascript.com)
 
@@ -1170,6 +1170,7 @@
 1528|[Shuffle String](./solutions/1528-shuffle-string.js)|Easy|
 1529|[Minimum Suffix Flips](./solutions/1529-minimum-suffix-flips.js)|Medium|
 1530|[Number of Good Leaf Nodes Pairs](./solutions/1530-number-of-good-leaf-nodes-pairs.js)|Medium|
+1531|[String Compression II](./solutions/1531-string-compression-ii.js)|Hard|
 1534|[Count Good Triplets](./solutions/1534-count-good-triplets.js)|Easy|
 1535|[Find the Winner of an Array Game](./solutions/1535-find-the-winner-of-an-array-game.js)|Medium|
 1550|[Three Consecutive Odds](./solutions/1550-three-consecutive-odds.js)|Easy|

solutions/1531-string-compression-ii.js

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+/**
+ * 1531. String Compression II
+ * https://leetcode.com/problems/string-compression-ii/
+ * Difficulty: Hard
+ *
+ * Run-length encoding is a string compression method that works by replacing consecutive
+ * identical characters (repeated 2 or more times) with the concatenation of the character
+ * and the number marking the count of the characters (length of the run). For example,
+ * to compress the string "aabccc" we replace "aa" by "a2" and replace "ccc" by "c3". Thus
+ * the compressed string becomes "a2bc3".
+ *
+ * Notice that in this problem, we are not adding '1' after single characters.
+ *
+ * Given a string s and an integer k. You need to delete at most k characters from s such that
+ * the run-length encoded version of s has minimum length.
+ *
+ * Find the minimum length of the run-length encoded version of s after deleting at most
+ * k characters.
+ */
+
+/**
+ * @param {string} s
+ * @param {number} k
+ * @return {number}
+ */
+var getLengthOfOptimalCompression = function(s, k) {
+  const n = s.length;
+  const dp = new Array(n + 1).fill().map(() => new Array(k + 1).fill(9999));
+  dp[0][0] = 0;
+
+  for (let i = 1; i <= n; i++) {
+    for (let j = 0; j <= k; j++) {
+      let count = 0;
+      let deletions = 0;
+
+      for (let m = i; m >= 1; m--) {
+        if (s[m - 1] === s[i - 1]) count++;
+        else deletions++;
+
+        if (j - deletions >= 0) {
+          dp[i][j] = Math.min(
+            dp[i][j],
+            dp[m - 1][j - deletions] + calculateEncodedLength(count)
+          );
+        }
+      }
+
+      if (j > 0) {
+        dp[i][j] = Math.min(dp[i][j], dp[i - 1][j - 1]);
+      }
+    }
+  }
+
+  return dp[n][k];
+
+  function calculateEncodedLength(count) {
+    if (count === 0) return 0;
+    if (count === 1) return 1;
+    if (count < 10) return 2;
+    if (count < 100) return 3;
+    return 4;
+  }
+};