insert-delete-getrandom-o1
// 参考了下面一些讨论的解法
// https://discuss.leetcode.com/topic/53235/java-with-hashtable-arraylist/2 class RandomizedSet {
vector<int> vec;
unordered_map<int, int> umap;
public:
/** Initialize your data structure here. */
RandomizedSet() { } /** Inserts a value to the set. Returns true if the set did not already contain the specified element. */
bool insert(int val) {
if (umap.find(val) != umap.end()) {
return false;
}
umap[val] = vec.size();
vec.push_back(val);
return true;
} /** Removes a value from the set. Returns true if the set contained the specified element. */
bool remove(int val) {
if (umap.find(val) == umap.end()) {
return false;
}
int pos = umap[val];
int back = vec.back();
umap[back] = pos;
vec[pos] = back;
vec.erase(vec.begin()+vec.size()-);
umap.erase(val);
return true;
} /** Get a random element from the set. */
int getRandom() {
int randpos = rand() % vec.size();
return vec[randpos];
}
}; /**
* Your RandomizedSet object will be instantiated and called as such:
* RandomizedSet obj = new RandomizedSet();
* bool param_1 = obj.insert(val);
* bool param_2 = obj.remove(val);
* int param_3 = obj.getRandom();
*/
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