axross
diff --git a/‎solutions/count_vowels_permutation.ts
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+35Lines changed: 35 additions & 0 deletions b/‎solutions/count_vowels_permutation.ts
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+35Lines changed: 35 additions & 0 deletions
diff --git a/‎solutions/count_vowels_permutation_test.ts
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+12Lines changed: 12 additions & 0 deletions b/‎solutions/count_vowels_permutation_test.ts
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+12Lines changed: 12 additions & 0 deletions
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+// 1220. Count Vowels Permutation
+// https://leetcode.com/problems/count-vowels-permutation/
+export default function countVowelPermutation(n: number): number {
+  function traverse(nextChars: string[], n: number): number {
+    if (n === 0) return 1;
+
+    let permutation = 0;
+
+    for (const char of nextChars) {
+      const key = `${char}*${n}`;
+
+      if (!memo.has(key)) {
+        memo.set(key, traverse(NEXT_CHARS_EACH_CHAR.get(char), n - 1));
+      }
+
+      permutation += memo.get(key);
+    }
+
+    return permutation % DIVISOR;
+  }
+
+  return traverse(["a", "e", "i", "o", "u"], n);
+}
+
+const memo = new Map();
+
+const DIVISOR = 1e9 + 7;
+
+const NEXT_CHARS_EACH_CHAR = new Map([
+  ["a", ["e"]],
+  ["e", ["a", "i"]],
+  ["i", ["a", "e", "o", "u"]],
+  ["o", ["i", "u"]],
+  ["u", ["a"]]
+]);
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+import { test } from "https://deno.land/std/testing/mod.ts";
+import { assertStrictEq } from "https://deno.land/std/testing/asserts.ts";
+import countVowelPermutation from "./count_vowels_permutation.ts";
+
+test("1220. Count Vowels Permutation", () => {
+  assertStrictEq(countVowelPermutation(1), 5);
+  assertStrictEq(countVowelPermutation(2), 10);
+  assertStrictEq(countVowelPermutation(5), 68);
+  assertStrictEq(countVowelPermutation(144), 18208803);
+  assertStrictEq(countVowelPermutation(2000), 793084836);
+  assertStrictEq(countVowelPermutation(0), 1);
+});