I have observed a fact while solving . The complexity of lower bound varies with type of iterator passed to it.

But a more weird fact is
1. the below lower bound takes O(log(n)) time
~~~~~ multiset< ll > set1; //some insert operation on multiset it=set1.lower_bound(val); ~~~~~

the question is Vasiliy's Multiset

here is my submission in which it took O(logn) when i used in above format here
2. the below lower bound works in O(n) time

multiset< ll > set1;
//some insert operation on multiset
it=lower_bound(set1.begin(),set1.end(),val);

here is my submission in which it took O(n) when i used in above format here
[cut] I dont understand why it was happening like this because both iterators here are same type.

Can someone specify places where all places lower_bound function is of O(logn) complexity