- map的find函数,找不到会返回end()
- vector的emplace_back()函数,比push_back可以减少一次复制,强烈推荐
- map的erase函数,删除key,在迭代时注意
/*
* @lc app=leetcode id=380 lang=cpp
*
* [380] Insert Delete GetRandom O(1)
*/
// @lc code=start
class RandomizedSet {
private:
vector<int> nums;
unordered_map<int,int> mp;
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(mp.find(val) != mp.end()) return false;
nums.emplace_back(val);
mp[val] = nums.size() - 1;
return true;
}
/** Removes a value from the set. Returns true if the set contained the specified element. */
bool remove(int val) {
if(mp.find(val) == mp.end()) return false;
nums[mp[val]] = nums.back();
mp[nums.back()] = mp[val];
nums.pop_back();
mp.erase(val);
return true;
}
/** Get a random element from the set. */
int getRandom() {
return nums[rand() % nums.size()];
}
};
/**
* 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();
*/
// @lc code=end