Answer by Mehtab Butt for How to find if a given key exists in a std::map
Both find() and contains() can be used. According to the documentation. Both methods take constant time on average and linear time in the worst case.
View ArticleAnswer by NutCracker for How to find if a given key exists in a std::map
I know this question already has some good answers but I think my solution is worth of sharing.It works for both std::map and std::vector<std::pair<T, U>> and is available from...
View ArticleAnswer by WBuck for How to find if a given key exists in a std::map
C++17 simplified this a bit more with an If statement with initializer.This way you can have your cake and eat it too.if ( auto it{ m.find( "key" ) }; it != std::end( m ) ) { // Use `structured...
View ArticleAnswer by Denis Sablukov for How to find if a given key exists in a std::map
C++20 gives us std::map::contains to do that.#include <iostream>#include <string>#include <map>int main(){ std::map<int, std::string> example = {{1, "One"}, {2, "Two"}, {3,...
View ArticleAnswer by Muhammad Ahmad Zafar for How to find if a given key exists in a...
map <int , char>::iterator itr; for(itr = MyMap.begin() ; itr!= MyMap.end() ; itr++) { if (itr->second == 'c') { cout<<itr->first<<endl; } }
View ArticleAnswer by Lambage for How to find if a given key exists in a std::map
template <typename T, typename Key>bool key_exists(const T& container, const Key& key){ return (container.find(key) != std::end(container));}Of course if you wanted to get fancier you...
View ArticleAnswer by EmreS for How to find if a given key exists in a std::map
If you want to compare pair of map you can use this method:typedef map<double, double> TestMap;TestMap testMap;pair<map<double,double>::iterator,bool>...
View ArticleAnswer by Hope for How to find if a given key exists in a std::map
Comparing the code of std::map::find and std::map::count, I'd say the first may yield some performance advantage:const_iterator find(const key_type& _Keyval) const { // find an element in...
View ArticleAnswer by hustljian for How to find if a given key exists in a std::map
map<string, string> m;check key exist or not, and return number of occurs(0/1 in map):int num = m.count("f"); if (num>0) { //found } else { // not found }check key exist or not, and return...
View ArticleAnswer by DavidRR for How to find if a given key exists in a std::map
To check if a particular key in the map exists, use the count member function in one of the following ways:m.count(key) > 0m.count(key) == 1m.count(key) != 0The documentation for map::find says:...
View ArticleAnswer by Invictus for How to find if a given key exists in a std::map
Be careful in comparing the find result with the the end like for map 'm' as all answer have done above map::iterator i = m.find("f"); if (i == m.end()) { } else { } you should not try and perform any...
View ArticleAnswer by aJ. for How to find if a given key exists in a std::map
m.find == m.end() // not found If you want to use other API, then find go for m.count(c)>0 if (m.count("f")>0) cout << " is an element of m.\n"; else cout << " is not an element of...
View ArticleAnswer by anon for How to find if a given key exists in a std::map
Use map::find and map::end:if (m.find("f") == m.end()) { // not found} else { // found}
View ArticleAnswer by Steve Jessop for How to find if a given key exists in a std::map
I think you want map::find. If m.find("f") is equal to m.end(), then the key was not found. Otherwise, find returns an iterator pointing at the element found.The error is because p.first is an...
View ArticleAnswer by Andreas Bonini for How to find if a given key exists in a std::map
You can use .find():map<string,string>::iterator i = m.find("f");if (i == m.end()) { /* Not found */ }else { /* Found, i->first is f, i->second is ++-- */ }
View ArticleHow to find if a given key exists in a std::map
I'm trying to check if a given key is in a map and somewhat can't do it:typedef map<string,string>::iterator mi;map<string, string> m;m.insert(make_pair("f","++--"));pair<mi,mi> p =...
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