551. Student Attendance Record I

/**
 * 551. Student Attendance Record I
 * You are given a string s representing an attendance record for a student 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.
The 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.
Return true if the student is eligible for an attendance award, or false otherwise.

Example 1:
Input: s = "PPALLP"
Output: true
Explanation: The student has fewer than 2 absences and was never late 3 or more consecutive days.

Example 2:
Input: s = "PPALLL"
Output: false
Explanation: The student was late 3 consecutive days in the last 3 days, so is not eligible for the award.
 *
*/
#include <iostream>
using namespace std;

/**
 * Solution: keep tracking letter and count it
 * Time complexity: O(n)
 * Space complexity: O(1)
 * 
*/
class Solution
{
public:
    bool checkRecord(string s)
    {
        int size = s.size();
        if (size == 0)
        {
            return false;
        }
        int absent_count = 0;
        for (size_t i = 0; i < size; i++)
        {
            char ch = s[i];
            if (ch == 'A')
            {
                absent_count += 1;
                if (absent_count >= 2)
                {
                    return false;
                }
            }
            else if (ch == 'L' && i + 2 <= size - 1)
            {
                if (s[i + 1] == 'L' && s[i + 2] == 'L')
                {
                    return false;
                }
            }
        }
        return true;
    }
};