Published Jun 01, 2022
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Implement the RandomizedSet class:
RandomizedSet() Initializes the RandomizedSet object.bool insert(int val) Inserts an item val into the set if not present. Returns true if the item was not present, false otherwise.bool remove(int val) Removes an item val from the set if present. Returns true if the item was present, false otherwise.int getRandom() Returns a random element from the current set of elements
(it’s guaranteed that at least one element exists when this method is
called). Each element must have the same probability of being returned.You must implement the functions of the class such that each function works in average O(1) time complexity.
Input
["RandomizedSet", "insert", "remove", "insert", "getRandom", "remove", "insert", "getRandom"]
[[], [1], [2], [2], [], [1], [2], []]
Output
[null, true, false, true, 2, true, false, 2]
Explanation
RandomizedSet randomizedSet = new RandomizedSet();
randomizedSet.insert(1); // Inserts 1 to the set. Returns true as 1 was inserted successfully.
randomizedSet.remove(2); // Returns false as 2 does not exist in the set.
randomizedSet.insert(2); // Inserts 2 to the set, returns true. Set now contains [1,2].
randomizedSet.getRandom(); // getRandom() should return either 1 or 2 randomly.
randomizedSet.remove(1); // Removes 1 from the set, returns true. Set now contains [2].
randomizedSet.insert(2); // 2 was already in the set, so return false.
randomizedSet.getRandom(); // Since 2 is the only number in the set, getRandom() will always return 2.
-2^31 <= val <= 2^31 - 12 * 10^5 calls will be made to insert, remove, and getRandom.getRandom is called.getRandom requires an array to store the valuesO(1) deletion requires a map to store value to indexclass RandomizedSet {
valueToIndex: Map<number, number>;
valuesArray: number[];
constructor() {
this.valueToIndex = new Map<number, number>();
this.valuesArray = []
}
insert(val: number): boolean {
const hasVal: boolean = this.valueToIndex.has(val)
if(!hasVal){
this.valuesArray.push(val);
this.valueToIndex.set(val, this.valuesArray.length - 1)
}
return !hasVal
}
remove(val: number): boolean {
const hasVal: boolean = this.valueToIndex.has(val)
if(hasVal){
const valIndex: number = this.valueToIndex.get(val)
const lastVal: number = this.valuesArray[this.valuesArray.length - 1];
// replace removed value with last & update index
this.valuesArray[valIndex] = lastVal
this.valueToIndex.set(lastVal, valIndex);
// remove last
this.valuesArray.pop();
// update map
this.valueToIndex.delete(val);
}
return hasVal;
}
getRandom(): number {
return this.valuesArray[Math.floor(Math.random()*this.valuesArray.length)]
}
}
/**
* Your RandomizedSet object will be instantiated and called as such:
* var obj = new RandomizedSet()
* var param_1 = obj.insert(val)
* var param_2 = obj.remove(val)
* var param_3 = obj.getRandom()
*/