One way would be to convert the arrays to JSON strings, then use a Set to get unique values, and convert back again var arr = [ [1, 1, 2], [1, 2, 1], [1, 1, 2], [1, 2, 1], [2, 1, 1], [2, 1, 1] ]; let set = new Set(arr.map(JSON.stringify)); let arr2 = Array.from(set).map(JSON.parse); … Read more
Actually, there is a way to do this. Since kernel 3.3 with CONFIG_CHECKPOINT_RESTORE set(which is set in most distros), there is /proc/sys/kernel/ns_last_pid which contains last pid generated by kernel. So, if you want to set PID for forked program, you need to perform these actions: Open /proc/sys/kernel/ns_last_pid and get fd flock it with LOCK_EX write … Read more
Suppose you label all the input sets. A={1, 2, 3}, B={1, 2}, C={2, 3}, D={2, 4}, E={} Now build intermediate sets, one per element in the universe, containing the labels of the sets where it appears: 1={A,B} 2={A,B,C,D} 3={A,C} 4={D} Now for each input set compute the intersection of all the label sets of its … Read more
The problem being solved is that the previous hash algorithm in Lib/sets.py had horrendous performance on datasets that arise in a number of graph algorithms (where nodes are represented as frozensets): # Old-algorithm with bad performance def _compute_hash(self): result = 0 for elt in self: result ^= hash(elt) return result def __hash__(self): if self._hashcode is … Read more
It will work out of the box, however, there might be cases, when it makes sense to overload __eq__, __ne__ and __hash__. By default, __eq__ will compare for object identity. This might not be what you want. In that case, you have to take care that equal object have equal hashes, and, ideally, not equal … Read more
The individual items that you put into a set can’t be mutable, because if they changed, the effective hash would change and thus the ability to check for inclusion would break down. Instead, you need to put immutable objects into a set – e.g. frozensets. If you change the return statement from your enum method … Read more
Simpler Java-8 solution involving Collectors.toMap: Map<Integer, String> mapFromSet = set.stream() .collect(Collectors.toMap(Entry::getKey, Entry::getValue)); An IllegalStateException will be thrown if duplicate key is encountered.
Nope, you’ve found exactly the solution you’re supposed to use. Even for TreeSet, it’s frowned upon to use comparison criteria that aren’t compatible with equals: Note that the ordering maintained by a sorted set (whether or not an explicit comparator is provided) must be consistent with equals if the sorted set is to correctly implement … Read more
It doesn’t cause a crash, it just doesn’t compile. set doesn’t have access by index. You can get the nth element like this: std::set<int>::iterator it = my_set.begin(); std::advance(it, n); int x = *it; Assuming my_set.size() > n, of course. You should be aware that this operation takes time approximately proportional to n. In C++11 there’s … Read more
Per the C++ standard, iteration over the elements in an std::set proceeds in sorted order as determined by std::less or by the optional comparison predicate template argument. (Also per the C++ standard, insertion, lookup and deletion take at most O(lg n) time, so balanced search trees are currently the only viable implementation choice for std::set, … Read more