Set - Google Top Interview Questions

                        Solution in C++ :

class CustomSet {
    int S = 1e3;
    vector<list<int>> v;
    hash<int> hs;

    public:
    CustomSet() {
        v.resize(S);
    }

    void add(int val) {
        if (exists(val)) return;
        int id = hs(val) % S;
        v[id].push_back(val);
    }

    bool exists(int val) {
        int id = hs(val) % S;
        for (int x : v[id]) {
            if (x == val) return true;
        }
        return false;
    }

    void remove(int val) {
        int id = hs(val) % S;
        for (auto it = v[id].begin(); it != v[id].end(); it++) {
            if (*it == val) {
                v[id].erase(it);
                return;
            }
        }
    }
};
                    

                        Solution in Java :

import java.util.*;

class CustomSet {
    ArrayList<Integer>[] buckets;
    int T;
    public CustomSet() {
        T = 300;

        buckets = new ArrayList[T];
    }

    public void add(int val) {
        if (!exists(val)) {
            buckets[map(val)].add(val);
        }
    }

    public boolean exists(int val) {
        int m = map(val);
        if (buckets[m] == null)
            buckets[m] = new ArrayList<Integer>();
        return buckets[m].contains(val);
    }

    public void remove(int val) {
        if (exists(val))
            buckets[map(val)].remove(Integer.valueOf(val));
    }

    public int map(int val) {
        return ((val % T) + T) % T;
    }
}
                    

                        Solution in Python : 
                            
class ListNode:
    def __init__(self, val):
        self.val = val
        self.next = None


class CustomSet:
    def __init__(self):
        self.mod = 2069  # any large prime number
        self.lst = [None] * self.mod

    def add(self, val):
        hashkey = val % self.mod
        if not self.lst[hashkey]:
            self.lst[hashkey] = ListNode(val)
        else:
            curr = self.lst[hashkey]
            while curr.next:
                if curr.val == val:
                    return
                curr = curr.next
            if curr.val == val:
                return
            curr.next = ListNode(val)

    def exists(self, val):
        hashkey = val % self.mod
        if self.lst[hashkey]:
            curr = self.lst[hashkey]
            while curr:
                if curr.val == val:
                    return True
                curr = curr.next
        return False

    def remove(self, val):
        hashkey = val % self.mod
        if self.lst[hashkey]:
            curr = self.lst[hashkey]
            if curr.val == val:
                self.lst[hashkey] = curr.next
                return
            while curr.next:
                if curr.next.val == val:
                    curr.next = curr.next.next
                    return
                curr = curr.next