Leetcode 380 Solution

This article provides solution to leetcode question 380 (insert-delete-getrandom-o1)
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https://leetcode.com/problems/insert-delete-getrandom-o1

Solution

class RandomizedSet {
    unordered_map<int, int> m;
    vector<int> v;

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 (m.find(val) != m.end())
            return false;

        m[val] = v.size();
        v.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 (m.find(val) == m.end())
            return false;

        int i = m[val];
        swap(v[i], v.back());
        m[v[i]] = i;

        m.erase(val);
        v.pop_back();

        return true;
    }

    /** Get a random element from the set. */
    int getRandom() {
        if (v.size() == 0)
            return -1;

        return v[rand() % v.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();
 */