How to check if std map contains a key without doing insert

Question

The only way I have found to check for duplicates is by inserting and checking the std  pair second for false  but the problem is that this still inserts something if the key is unused  whereas what I want is a map contains key   function

User · Accepted Answer

Use my map count  key    it can only return 0 or 1  which is essentially the Boolean result you want   Alternately my map find  key      my map end   works too

User · Answer

Potatoswatter s answer is all right  but I prefer to use find or lower bound instead  lower bound is especially useful because the iterator returned can subsequently be used for a hinted insertion  should you wish to insert something with the same key   map lt K  V gt   iterator iter my map lower bound key    if  iter    my map end      key  lt  iter- gt first          not found                my map insert iter  make pair key  value           hinted insertion   else              use iter- gt second here

User · Answer

Your desideratum map contains key   is scheduled for the draft standard C  2a   In 2017 it was implemented by gcc 9 2   It s also in the current clang

[c++] How to check if std::map contains a key without doing insert?

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