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程式語言 - LeetCode - C++ - 380. Insert Delete GetRandom O(1)

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參考資訊：
https://www.cnblogs.com/grandyang/p/5740864.html

題目：


解答：

class RandomizedSet {
private:
    vector<int> nums;
    unordered_map<int, int> mp;

public:
    RandomizedSet() {
    }
    
    bool insert(int val) {
        if (mp.count(val)) {
            return false;
        }

        nums.push_back(val);
        mp[val] = nums.size() - 1;
        return true;
    }
    
    bool remove(int val) {
        if (!mp.count(val)) {
            return false;
        }

        int idx = mp[val];
        int last = nums.back();

        nums[idx] = last;
        mp[last] = idx;

        nums.pop_back();
        mp.erase(val);
        return true;
    }
    
    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();
 */