HashSet

C++

Java

Python3

include

#include <unordered_set>

import java.util.*;

new

std::unordered_set<int> s;

Set<Integer> s = new HashSet<>();

s = set()

add

s.insert(x);

s.add(x);

s.add(x)

delete

s.erase(x);

s.remove(x);

s.discard(x)

check in set

std::unordered_set<int>::const_iterator it = s.find(x);
if (it != s.end())

if (s.contains(x))

if x in s:

size

s.size()

s.size()

len(s)

check empty

if (s.empty())

if (s.isEmpty())

if not s: