Add solution #2645

Author: JoshCrozier

README.md

@@ -1965,6 +1965,7 @@
 2641|[Cousins in Binary Tree II](./solutions/2641-cousins-in-binary-tree-ii.js)|Medium|
 2643|[Row With Maximum Ones](./solutions/2643-row-with-maximum-ones.js)|Easy|
 2644|[Find the Maximum Divisibility Score](./solutions/2644-find-the-maximum-divisibility-score.js)|Easy|
+2645|[Minimum Additions to Make Valid String](./solutions/2645-minimum-additions-to-make-valid-string.js)|Medium|
 2648|[Generate Fibonacci Sequence](./solutions/2648-generate-fibonacci-sequence.js)|Easy|
 2649|[Nested Array Generator](./solutions/2649-nested-array-generator.js)|Medium|
 2650|[Design Cancellable Function](./solutions/2650-design-cancellable-function.js)|Hard|

solutions/2645-minimum-additions-to-make-valid-string.js

@@ -0,0 +1,49 @@
+/**
+ * 2645. Minimum Additions to Make Valid String
+ * https://leetcode.com/problems/minimum-additions-to-make-valid-string/
+ * Difficulty: Medium
+ *
+ * Given a string word to which you can insert letters "a", "b" or "c" anywhere and any number
+ * of times, return the minimum number of letters that must be inserted so that word becomes valid.
+ *
+ * A string is called valid if it can be formed by concatenating the string "abc" several times.
+ */
+
+/**
+ * @param {string} word
+ * @return {number}
+ */
+var addMinimum = function(word) {
+  let result = 0;
+  let index = 0;
+
+  while (index < word.length) {
+    if (word[index] === 'a') {
+      if (word[index + 1] === 'b' && word[index + 2] === 'c') {
+        index += 3;
+      } else if (word[index + 1] === 'b') {
+        result += 1;
+        index += 2;
+      } else if (word[index + 1] === 'c') {
+        result += 1;
+        index += 2;
+      } else {
+        result += 2;
+        index += 1;
+      }
+    } else if (word[index] === 'b') {
+      if (word[index + 1] === 'c') {
+        result += 1;
+        index += 2;
+      } else {
+        result += 2;
+        index += 1;
+      }
+    } else {
+      result += 2;
+      index += 1;
+    }
+  }
+
+  return result;
+};