Add soution 551

Author: vulgur

Diff for: 551_StudentAttendanceRecord1.swift

@@ -0,0 +1,27 @@
+class Solution {
+    func checkRecord(_ s: String) -> Bool {
+        var absents = 0
+        var lates = 0
+        var lastRecord: Character = "L"
+        for record in s {
+            if record == "A" {
+                absents += 1
+                if absents > 1 {
+                    return false
+                }
+            } else if record == "L" {
+                if lastRecord == "L" {
+                    lates += 1
+                } else {
+                    lates = 1
+                }
+
+                if lates > 2 {
+                    return false
+                }
+            }
+            lastRecord = record
+        }
+        return true
+    }
+}