Create 552. Student Attendance Record II (#489)

Author: Chayandas07

552. Student Attendance Record II

@@ -0,0 +1,46 @@
+class Solution {
+  // Helper function to recursively count valid attendance records
+    int solve(int index, int n, int absCount, int lateCount, vector<vector<vector<int>>>& dp) {
+        const int MOD = 1e9 + 7;  // Define the modulo constant
+
+        // Base case: If we've reached the end of the attendance record, return 1
+        if (index >= n) {
+            return 1;
+        }
+
+        // If the result is already computed, return the cached value
+        if (dp[index][absCount][lateCount] != -1) {
+            return dp[index][absCount][lateCount];
+        }
+
+        int ans = 0;  // Initialize the answer for this state
+
+        // Absent module: If absences are less than 1, we can add an 'A'
+        if (absCount < 1) {
+            ans = ((ans % MOD) + solve(index + 1, n, absCount + 1, 0, dp) % MOD) % MOD;
+        }
+
+        // Late module: If consecutive lates are less than 2, we can add an 'L'
+        if (lateCount < 2) {
+            ans = ((ans % MOD) + solve(index + 1, n, absCount, lateCount + 1, dp) % MOD) % MOD;
+        }
+
+        // Present module: We can always add a 'P'
+        ans = ((ans % MOD) + solve(index + 1, n, absCount, 0, dp) % MOD) % MOD;
+
+        // Store the result in the dp array and return it
+        return dp[index][absCount][lateCount] = ans;
+    }
+public:
+    int checkRecord(int n) {
+        int absCount=0;
+        int lateCount=0;
+        int index=0;
+        // Initialize a 3D dp array with dimensions [n][2][3] and all values set to -1
+        vector<vector<vector<int>>> dp(n, vector<vector<int>>(2, vector<int>(3, -1)));
+
+        // Call the solve function starting from index 0 with 0 absences and 0 lates
+        return solve(index,n,absCount,lateCount,dp);
+        
+    }
+};