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Daily Coding Challenge #32

wingkwong profile image wkw ・2 min read

About

This is a series of Daily Coding Challenge. Each day I show a few solutions written in C++. The questions are from coding practice/contest sites such as HackerRank, LeetCode, Codeforces, Atcoder and etc.


/*
LeetCode - Insert Delete GetRandom O(1)

Design a data structure that supports all following operations in average O(1) time.

insert(val): Inserts an item val to the set if not already present.
remove(val): Removes an item val from the set if present.
getRandom: Returns a random element from current set of elements. Each element must have the same probability of being returned.
Example:

// Init an empty set.
RandomizedSet randomSet = new RandomizedSet();

// Inserts 1 to the set. Returns true as 1 was inserted successfully.
randomSet.insert(1);

// Returns false as 2 does not exist in the set.
randomSet.remove(2);

// Inserts 2 to the set, returns true. Set now contains [1,2].
randomSet.insert(2);

// getRandom should return either 1 or 2 randomly.
randomSet.getRandom();

// Removes 1 from the set, returns true. Set now contains [2].
randomSet.remove(1);

// 2 was already in the set, so return false.
randomSet.insert(2);

// Since 2 is the only number in the set, getRandom always return 2.
randomSet.getRandom();
*/

class RandomizedSet {
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) {
        for(int i=0;i<s.size();i++){
            if(s[i]==val) return false;
        }
        s.push_back(val);
        return true;
    }

    /** Removes a value from the set. Returns true if the set contained the specified element. */
    bool remove(int val) {
        for(int i=0;i<s.size();i++){
            if(s[i]==val) {
                s.erase(s.begin()+i);
                return true;
            }
        }
        return false;
    }

    /** Get a random element from the set. */
    int getRandom() {
        return s[rand()%s.size()];
    }
private:
    vector<int> s;
};

/**
 * 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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The source code is available in corresponding repo below. Star and watch for timely updates!

GitHub logo wingkwong / leetcode

Migrated to https://github.com/wingkwong/competitive-programming

GitHub logo wingkwong / hackerrank

Migrated to https://github.com/wingkwong/competitive-programming

GitHub logo wingkwong / codeforces

Migrated to https://github.com/wingkwong/competitive-programming

GitHub logo wingkwong / atcoder

Migrated to https://github.com/wingkwong/competitive-programming

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