Inserting in a multiset: before the first occurence of that value instead of after the last occurence

Question

As the title says multiset inserts a value at the end of the range of all the same values.

(Ex: Inserting 2 in a multiset 1,2,2,3 makes it 1,2,2,/*new*/ 2,3).

How do I get the new value inserted at the start of the range of all the same values?

(Ex: Inserting 2 in multiset 1,2,2,3 should make 1,/*new*/ 2,2,2,3)

Can't you reverse the whole multiset? `std::multiset>` and use `reverse_iterator` for iteration? — Jarod42, Jul 30 '19 at 11:39
Well given it has other uses I don't think it a good solution. @Jarod42 — gst1502, Jul 30 '19 at 11:43
Better example would be with `std::pair` comparing only `ValueType` as for `int`, it doesn't really matter. — Jarod42, Jul 30 '19 at 11:43
@Jarod42 https://coliru.stacked-crooked.com/a/4b8bf82c66662e8d — jrok, Jul 30 '19 at 11:52

score 5 · Accepted Answer · answered Jul 30 '19 at 11:38

Try this

std::multiset<int> mset { 2,4,5,5,6,6 }; 
int val = 5;
auto it = mset.equal_range ( val ).first; //Find the first occurrence of your target value.  Function will return an iterator

mset.insert ( it, val );  //insert the value using the iterator

score 2 · Answer 2 · answered Jul 30 '19 at 11:39

2

Use the function insert(iterator hint, const value_type& value) instead of insert(const value_type& value). As per documentation, this will insert before the hint. You can use std::multiset::equal_range to get the iterator to the lower bound.

answered Jul 30 '19 at 11:39

eerorika

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Inserting in a multiset: before the first occurence of that value instead of after the last occurence

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