Leetcode: Attendance record for students | "551"

tag: PPA int resolves the problem of emptying a matching regular expression loop string

Leetcode: Attendance record of Students | "551" topic description

Given a string to represent a student's attendance record, this record contains only the following three characters:

1. ' A ': Absent, absence
2. ' L ': late, late
3. ' P ': Present, on the scene

If a student's attendance record does not exceed a ' a ' (absence) and does not exceed two consecutive ' L ' (late), then the student will be rewarded.

You need to judge whether he will be rewarded according to the student's attendance record.

Example 1:

Input: "PPALLP" output: True

Example 2:

Input: "ppalll" output: False

Problem analysis

For string problems, we need to reflect on the so-called rock-regular expression .

Many problems can be solved quickly, because we are suffering too little, so it backfired.

　　l{3,} can represent 3 consecutive and above L appear, a.*a can represent 2 times a , so if the regular match is successful, then it will not be rewarded!

Java

Class Solution {public    Boolean Checkrecord (String s)    {        if (s.matches (". *l{3,}.*"))            return false;        if (S.matches (". *a.*a.*"))            return false;        return true;    }}

But the above for This problem, the Regular expression solution is concise but not efficient .

We loop through the string once, a variable counts the number of times a, a variable counts the number of consecutive L times, there is a technique for successive times, when the first L is encountered, the next is not L, and the count variable is emptied immediately .

public Boolean Checkrecord (String s) {        int a = 0;        int l = 0;        for (char C:s.tochararray ())        {            if (c== ' A ')                a++;            if (c== ' L ')                l++;            else                l=0;            if (a>1| | l>=3)                return false;        }        return true;    }

　　

Leetcode: Attendance record for students | "551"