题目描述：

You are given a string representing an attendance record for a student. The record only contains the following three characters:

  1. ‘A’ : Absent.
  2. ‘L’ : Late.
  3. ‘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

题目很简单，就是扫一遍字符串就可以了，但是要注意一些边界情况。

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class Solution {
public:
    bool checkRecord(string s) {
        int acnt = 0;
        for (int i = 0; i + 2 < s.length(); i++) {
            if (s[i] == 'A') {
                acnt++;
                if (acnt > 1) return false;
            }
            else if (s[i] == 'L' && s[i + 1] == 'L' && s[i + 2] == 'L') {
                return false;
            } 
        }
        
        for (int i = max(0, (int)s.length() - 2); i < s.length(); i++) {
            if (s[i] == 'A') {
                acnt++;
                if (acnt > 1) return false;
            }
        }
        return true;
        
    }
};