rationale for std::lower_bound and std::upper_bound?

Question

STL provides binary search functions std::lower_bound and std::upper_bound, but I tend not to use them because I\'ve been unable to remember what they do, because their contract

Answer 1

For an array or vector :

std::lower_bound: Returns an iterator pointing to the first element in the range that is

• less than or equal to value.(for array or vector in decreasing order)
• greater than or equal to value.(for array or vector in increasing order)

std::upper_bound: Returns an iterator pointing to the first element in the range that is

• less than value.(for array or vector in decreasing order)

• greater than value.(for array or vector in increasing order)