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

python solution: I imagined a fictive page at the start (page 0), and, if the n was even, I also imagined a fictive page at the end (increased the value of n).

def pageCount(n, p):
    if n % 2 == 0:
        n += 1
        
    left = p // 2
    right = (n - p) // 2
        
    return min(left, right)

Here is my c++ solution, you can watch the explanation here : https://youtu.be/1T650YeAwRI

int pageCount(int n, int p) {
    return min(p/2, n/2-p/2);
}

Constant time solution C++

int pageCount(int n, int p) {
    int ffront;
    int fback;
    if(n%2 == 0){
        fback = (int)ceil((n-p)/2.0);
    }
    else{
        fback = (int)floor((n-p)/2.0);
    }

ffront = (int)ceil((p-1)/2.0);
return min(ffront, fback);

}

* Constant time solution C++

• int pageCount(int n, int p) {
• int ffront;
• int fback;
• if(n%2 == 0){
• fback = (int)ceil((n-p)/2.0);
• }
• else{
• fback = (int)floor((n-p)/2.0);
• }
• ffront = (int)ceil((p-1)/2.0); return min(ffront, fback); }