Add solution #552

Author: JoshCrozier

README.md

@@ -437,6 +437,7 @@
 546|[Remove Boxes](./0546-remove-boxes.js)|Hard|
 547|[Number of Provinces](./0547-number-of-provinces.js)|Medium|
 551|[Student Attendance Record I](./0551-student-attendance-record-i.js)|Easy|
+552|[Student Attendance Record II](./0552-student-attendance-record-ii.js)|Hard|
 557|[Reverse Words in a String III](./0557-reverse-words-in-a-string-iii.js)|Easy|
 560|[Subarray Sum Equals K](./0560-subarray-sum-equals-k.js)|Medium|
 563|[Binary Tree Tilt](./0563-binary-tree-tilt.js)|Easy|

solutions/0552-student-attendance-record-ii.js

@@ -0,0 +1,42 @@
+/**
+ * 552. Student Attendance Record II
+ * https://leetcode.com/problems/student-attendance-record-ii/
+ * Difficulty: Hard
+ *
+ * An attendance record for a student can be represented as a string where each character
+ * signifies whether the student was absent, late, or present on that day. The record only
+ * contains the following three characters:
+ * - 'A': Absent.
+ * - 'L': Late.
+ * - 'P': Present.
+ *
+ * Any student is eligible for an attendance award if they meet both of the following
+ * criteria:
+ * - The student was absent ('A') for strictly fewer than 2 days total.
+ * - The student was never late ('L') for 3 or more consecutive days.
+ *
+ * Given an integer n, return the number of possible attendance records of length n that make
+ * a student eligible for an attendance award. The answer may be very large, so return it
+ * modulo 109 + 7.
+ */
+
+/**
+ * @param {number} n
+ * @return {number}
+ */
+var checkRecord = function(n) {
+  const MOD = 1e9 + 7;
+  const dp = [[1, 0, 0], [0, 0, 0]];
+
+  for (let i = 0; i < n; i++) {
+    const m = dp.map(row => [...row]);
+    dp[0][0] = (m[0][0] + m[0][1] + m[0][2]) % MOD;
+    dp[0][1] = m[0][0];
+    dp[0][2] = m[0][1];
+    dp[1][0] = (m[0][0] + m[0][1] + m[0][2] + m[1][0] + m[1][1] + m[1][2]) % MOD;
+    dp[1][1] = m[1][0];
+    dp[1][2] = m[1][1];
+  }
+
+  return (dp[0][0] + dp[0][1] + dp[0][2] + dp[1][0] + dp[1][1] + dp[1][2]) % MOD;
+};