Hello everyone! I am new to competitive coding and asking a rookie query in a blog for the first time so apologies in advance if anything is not according to norms.

I was solving this problem today 1284B - New Year and Ascent Sequence . Here is the editorial. Idea behind my solution is almost as in editorial. The issue is that my submission with custom function for upper_bound got tle verdict but when I used built in function for the same it got accepted.

I used the concept of binary search in my function so the overall complexity is still O(nlogn) which should get accepted(according to me).

ll mid;

while (l <= r)
{
    mid = (l+r)/2;
    if(maxv[mid] <= x)
    {
        l = mid + 1;

    }
    else
    {
        r = mid-1;
    }

}
return l;

86439737 is the submission which got tle. 86412015 is the submission which got accepted.

Thanks in advance!