[LeetCode] Add January 17.

pin3da · Jan 17, 2021 · 3037205 · 3037205
1 parent b87c1d3
commit 3037205
Showing 1 changed file with 25 additions and 0 deletions.
diff --git a/solved/LeetCode/Challenges/2020/January/17.kt b/solved/LeetCode/Challenges/2020/January/17.kt
@@ -0,0 +1,25 @@
+class Solution {
+  data class State(val n: Int, val last: Int)
+  val seen = mutableMapOf<State, Int>()
+
+  fun countVowelStrings(n: Int): Int {
+    return count(State(n, 0))
+  }
+
+  private fun count(s: State) : Int {
+    if (s.n == 0) {
+      return 1
+    }
+
+    if (seen.contains(s)) {
+      return seen[s]!!
+    }
+
+    var ans = 0
+    for (next in s.last..4) {
+      ans += count(State(s.n-1, next))
+    }
+    seen[s] = ans
+    return ans
+  }
+}