551. Student Attendance Record I

Description

You are given a string representing an attendance record for a student. The record only contains the following three characters:
'A' : Absent.
'L' : Late.
'P' : Present.
A student could be rewarded if his attendance record doesn't contain more than one 'A' (absent) or more than two continuous 'L' (late).

You need to return whether the student could be rewarded according to his attendance record.

Example 1:
Input: "PPALLP"
Output: True

Example 2:
Input: "PPALLL"
Output: False

Solution

Iterative

class Solution {
    public boolean checkRecord(String s) {
        int absentCount = 0;
        int continousLateCount = 0;
        for (int i = 0; i < s.length(); ++i) {
            char c = s.charAt(i);
            switch(c) {
                case 'A':
                    ++absentCount;
                    continousLateCount = 0;
                    if (absentCount > 1) {
                        return false;
                    }
                    break;
                case 'L':
                    ++continousLateCount;
                    if (continousLateCount > 2) {
                        return false;
                    }
                    break;
                case 'P':
                    continousLateCount = 0;
                    break;
                default:
                    return false;
            }
        }
        
        return true;
    }
}

Regex

原来可以用正则表达式，也是挺牛掰的。

public boolean checkRecord(String s) {
    return !s.matches(".*LLL.*|.*A.*A.*");
}