Python: Semi-short looping solution…

def workbook(_, k, arr):
  p = s = 0
  for i in arr:
    for j in range(0, i, k):
      p, s = ((p + 1, s + 1)
        if j < p + 1 <= min(i, j + k)
        else (p + 1, s)) 
  return s

Here's a semi-short, non-looping functional solution…

def workbook(_, k, arr):
    pg = lambda m: m[0]
    prob1 = lambda m: m[1][0]
    probN = lambda m: m[1][1]
    return sum(map(
        lambda pgProbs: int(prob1(pgProbs) < pg(pgProbs) <= probN(pgProbs)), 
        enumerate(sum(map(
            lambda chNumProb: list(map(
                lambda pgProb1: (pgProb1, min(chNumProb, pgProb1 + k)), 
                range(0, chNumProb, k))), 
            arr), []), start=1))) 

It could be shorter, but I've seen people complain about the readability of functional code. So, I tried to make this descriptive. I used verbose names for lambda arguments. I also added lambdas for accessing the members of tuples returned from the inner map levels.

Here's a terse version of the same code…

def workbook(_, k, arr):
    return sum(map(lambda m: int(m[1][0] < m[0] <= m[1][1]),
            enumerate(sum(map(lambda i:
                list(map(lambda j: (j, min(i, j + k)), 
                range(0, i, k))), 
            arr), []), 1))) 

Here is problem solution in Python, Java, C++, C and Javascript - https://programmingoneonone.com/hackerrank-lisas-workbook-problem-solution.html

Here is my c++ solution

int workbook(int n, int k, vector arr) { vector> pages; int specialCount = 0;

for (int chapter = 0; chapter < n; chapter++) {
    int problems = arr[chapter];
    int problemNum = 1;

    while (problemNum <= problems) {
        int end = min(problemNum + k - 1, problems);
        vector<int> page;

        for (int i = problemNum; i <= end; i++) {
            page.push_back(i);
        }

        pages.push_back(page);
        problemNum = end + 1;
    }
}


for (int i = 0; i < pages.size(); i++) {
    int pageNumber = i + 1;
    for (int j=0;j<pages[i].size();j++) {
        if (pages[i][j] == pageNumber) {
            specialCount++;
        }
    }
}

return specialCount;

}

Here is my c++ solution , you can watch the explanation here : https://youtu.be/3L-haDbsjAg

int workbook(int n, int k, vector<int> arr) {
    int page = 1, chapter = 1, fe = 1, res = 0;
    while(chapter <= arr.size()){
        int le = min(fe + k - 1, arr[chapter-1]);
        if(fe <= page && page <= le) res++;
        fe = le + 1;
        if(fe > arr[chapter-1]) {
            chapter++;
            fe = 1;
        }
        page ++;
    }   
    return res;
}

Perl:

sub workbook {
    my ($n, $k, $arr) = @_;

    my @tmp;
    my $cnt = 0;
    my $j = 0;
    for (my $i = 0; $i < scalar(@$arr); $i++) {
        if ($arr->[$i] > $k) {
            for ($j = 1; $j <= $arr->[$i] - ($arr->[$i] % $k); $j += $k) {
                push(@tmp, [ $j..$j + $k - 1]);
            }
            push(@tmp, [$j..$arr->[$i]]) if ($arr->[$i] % $k != 0);
        } else { push(@tmp, [1..$arr->[$i]]); }
        
    }
    for (my $i = 0; $i <scalar(@tmp); $i++) {
        $cnt += grep { $_ == $i + 1} @{$tmp[$i]};
    }
    
    return $cnt;
}