Possible Duplicate:
How to find if a given key exists in a C++ std::map
In C++, how can I check if there is an element with a key?
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@Space_C0wb0y: Hardly. Learn the difference between a key and a value.Lightness Races in Orbit– Lightness Races in Orbit2011-05-06 13:36:53 +00:00Commented May 6, 2011 at 13:36
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Actually, the title of that question is misleading, it is indeed about finding whether a given key exists in a std::map.Tamás– Tamás2011-05-06 13:38:30 +00:00Commented May 6, 2011 at 13:38
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@Tomalak: Upon rereading the question and all answers, I am reasonably sure that it is a duplicate. Although the title is inaccurate.Björn Pollex– Björn Pollex2011-05-06 13:39:56 +00:00Commented May 6, 2011 at 13:39
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2 Answers
if (myMap.find(key) != myMap.end())
{ // there is such an element
}
See the reference for std::map::find
5 Comments
Lightness Races in Orbit
+1 (though I wouldn't recommend cplusplus.com to language newcomers).
Benoit
@Tomalak Geret'kal: are you sure that OP is a newcomer? And what would you recommend instead?
Ricko M
I am curious , what is so bad about cplusplus? I use it quite often to understand small bits.
Lightness Races in Orbit
The question rather gives it away.
Lightness Races in Orbit
@RickoM: cplusplus.com is notoriously error-ridden, and its tutorials are misleading (even for tutorials). I use it myself as a "reminder" reference, but I know C++ well enough to spot the mistakes, and absolutely would not recommend it.
Try to find it using the find method, which will return the end() iterator of your map if the element is not found:
if (data.find(key) != data.end()) {
// key is found
} else {
// key is not found
}
Of course you shouldn't find twice if you need the value corresponding to the given key later. In this case, simply store the result of find first:
YourMapType data;
...
YourMapType::const_iterator it;
it = data.find(key);
if (it != data.end()) {
// do whatever you want
}
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