I have run a benchmark on different data structures very recently at my company so I feel I need to drop a word. It is very complicated to benchmark something correctly. Benchmarking On the web, we rarely find (if ever) a well-engineered benchmark. Until today I only found benchmarks that were done the journalist way … Read more
The C++11 standard introduced uniform initialization which makes this much simpler if your compiler supports it: //myClass.hpp class myClass { private: static map<int,int> myMap; }; //myClass.cpp map<int,int> myClass::myMap = { {1, 2}, {3, 4}, {5, 6} }; See also this section from Professional C++, on unordered_maps.
As already mentioned, map allows to iterate over the elements in a sorted way, but unordered_map does not. This is very important in many situations, for example displaying a collection (e.g. address book). This also manifests in other indirect ways like: (1) Start iterating from the iterator returned by find(), or (2) existence of member … Read more
You have not initialized your inner map. Before your for loop you can add m[“uid”] = make(map[string]T) and then assign the name.
Almost. for(; iter != endIter; ) { if (Some Condition) { iter = aMap.erase(iter); } else { ++iter; } } What you had originally would increment the iterator twice if you did erase an element from it; you could potentially skip over elements that needed to be erased. This is a common algorithm I’ve seen … Read more
This can be accomplished by Unmarshaling into a map[string]json.RawMessage. var objmap map[string]json.RawMessage err := json.Unmarshal(data, &objmap) To further parse sendMsg, you could then do something like: var s sendMsg err = json.Unmarshal(objmap[“sendMsg”], &s) For say, you can do the same thing and unmarshal into a string: var str string err = json.Unmarshal(objmap[“say”], &str) EDIT: Keep … Read more
You can use c map (t => t.getP -> t) toMap but be aware that this needs 2 traversals.
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.
A Tree is just a restricted form of a Graph. Trees have direction (parent / child relationships) and don’t contain cycles. They fit with in the category of Directed Acyclic Graphs (or a DAG). So Trees are DAGs with the restriction that a child can only have one parent. One thing that is important to … Read more
You could use a Collector: import java.util.*; import java.util.stream.Collectors; public class Defensive { public static void main(String[] args) { Map<String, Column> original = new HashMap<>(); original.put(“foo”, new Column()); original.put(“bar”, new Column()); Map<String, Column> copy = original.entrySet() .stream() .collect(Collectors.toMap(Map.Entry::getKey, e -> new Column(e.getValue()))); System.out.println(original); System.out.println(copy); } static class Column { public Column() {} public Column(Column c) … Read more