Dependent Origination

how to sort an unordered_map?

Posted on: September 11, 2013

I googled around but then just realized what I should do when I want to, say, print the content of an unordered_map based on its keys:

unordered_map<int, int> counts;

map<int, int> ordered(counts.begin(), counts.end());

for(auto it = ordered.begin(0; it != ordered.end(); it++) {

output it


for some reason, probably due to the fact that i learned stl from examples, not really its implementation details (though I have spent quite some time reading about effective c++ a few times a few years later), it is very slow to dawn on me that stl::map is in fact a red-black tree that is sorted on its keys. that fact has always needed to come to me.


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September 2013
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