kt: add «552. Student Attendance Record II»

Signed-off-by: Matej Focko <me@mfocko.xyz>

kt/student-attendance-record-ii.kt

@@ -0,0 +1,43 @@
+val MOD = 1000000007
+
+class Solution {
+    private fun createState(): MutableList<MutableList<Int>> = (0..1).map { mutableListOf(0, 0, 0) }.toMutableList()
+
+    fun checkRecord(n: Int): Int {
+        val initialState = createState()
+        initialState[0][0] = 1
+
+        val finalState =
+            (1..n).fold(initialState) { state, _ ->
+                val nextState = createState()
+
+                (0..1).flatMap { absences -> (0..2).map { lates -> absences to lates } }.forEach { (absences, lates) ->
+                    nextState[absences][0] = (nextState[absences][0] + state[absences][lates]) % MOD
+
+                    if (absences < 1) {
+                        nextState[absences + 1][0] = (nextState[absences + 1][0] + state[absences][lates]) % MOD
+                    }
+
+                    if (lates < 2) {
+                        nextState[absences][lates + 1] = (nextState[absences][lates + 1] + state[absences][lates]) % MOD
+                    }
+                }
+
+                return@fold nextState
+            }
+
+        return finalState.fold(0) { acc, it ->
+            it.fold(acc) { acc, it ->
+                (acc + it) % MOD
+            }
+        }
+    }
+}
+
+fun main() {
+    val s = Solution()
+
+    check(s.checkRecord(2) == 8)
+    check(s.checkRecord(1) == 3)
+    check(s.checkRecord(10101) == 183236316)
+}