h3. 3. initializer lists

Simple one-line initializations with lists of constant values:

Simple one line initializations with lists of constant values:

== code(cpp) |
vector<pair<int, int>> dirs = {{-1, 0}, {0, -1}, {1, 0}, {0, 1}};

h3. 4. unordered_set, unordered_map

These are hash-based implementations of the well known $set$ and $map$ containers; the average time complexity on most operations is $O(1)$. (These containers were previously available on infoarena under $tr1$, but only a small fraction of users were actually using them.)
 
== code(cpp) |
unordered_map<string, int> age = {
  {"john", 18}, {"mary", 21}, {"anna", 19}
};
==

These are hash-based implementations of the well known $set$ and $map$ containers; the average time complexity on most operations is $O(1)$. (These containers were previously available on infoarena under tr1, but only a small fraction of users were actually using them.)