不使用任何内建的哈希表库设计一个哈希集合(HashSet)。
实现 MyHashSet
类:
void add(key)
向哈希集合中插入值key
。bool contains(key)
返回哈希集合中是否存在这个值key
。void remove(key)
将给定值key
从哈希集合中删除。如果哈希集合中没有这个值,什么也不做。
示例:
输入:
["MyHashSet", "add", "add", "contains", "contains", "add", "contains", "remove", "contains"]
[[], [1], [2], [1], [3], [2], [2], [2], [2]]
输出:
[null, null, null, true, false, null, true, null, false]
解释:
MyHashSet myHashSet = new MyHashSet();
myHashSet.add(1); // set = [1]
myHashSet.add(2); // set = [1, 2]
myHashSet.contains(1); // 返回 True
myHashSet.contains(3); // 返回 False ,(未找到)
myHashSet.add(2); // set = [1, 2]
myHashSet.contains(2); // 返回 True
myHashSet.remove(2); // set = [1]
myHashSet.contains(2); // 返回 False ,(已移除)
提示:
0 <= key <= 10^6
- 最多调用
10^4
次add
、remove
和contains
。
来源:力扣(LeetCode)
链接:https://leetcode-cn.com/problems/design-hashset
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解答
简单暴力:
class MyHashSet {
private:
vector<bool> map;
public:
/** Initialize your data structure here. */
MyHashSet() {
map.resize(1e6 + 1, false);
}
void add(int key) {
map[key] = true;
}
void remove(int key) {
map[key] = false;
}
/** Returns true if this set contains the specified element */
bool contains(int key) {
return map[key];
}
};
/**
* Your MyHashSet object will be instantiated and called as such:
* MyHashSet* obj = new MyHashSet();
* obj->add(key);
* obj->remove(key);
* bool param_3 = obj->contains(key);
*/
参照官方题解,哈希加链地址:
class MyHashSet {
private:
vector<list<int>> map;
// 质数求模
static const int base = 769;
static int hash(int key){
return key % base;
}
public:
/** Initialize your data structure here. */
MyHashSet() : map(base) {
}
void add(int key) {
int hashed_key = hash(key);
for(auto iter = map[hashed_key].begin(); iter != map[hashed_key].end(); iter++){
if((*iter) == key){
return;
}
}
map[hashed_key].push_back(key);
}
void remove(int key) {
int hashed_key = hash(key);
for(auto iter = map[hashed_key].begin(); iter != map[hashed_key].end(); iter++){
if((*iter)== key){
map[hashed_key].erase(iter);
return;
}
}
}
/** Returns true if this set contains the specified element */
bool contains(int key) {
int hashed_key = hash(key);
for(auto iter = map[hashed_key].begin(); iter != map[hashed_key].end(); iter++){
if((*iter) == key){
return true;
}
}
return false;
}
};
/**
* Your MyHashSet object will be instantiated and called as such:
* MyHashSet* obj = new MyHashSet();
* obj->add(key);
* obj->remove(key);
* bool param_3 = obj->contains(key);
*/