Insert Delete GetRandom O(1)

Statement

Implement a Random Set data structure that can perform the following operations:

• Init(): This initializes the Random Set object.
• Insert(): This function takes an integer, data, as its parameter and, if it does not already exist in the set, add it to the set, returning TRUE. If the integer already exists in the set, the function returns FALSE.
• Delete(): This function takes an integer, data, as its parameter and, if it exists in the set, removes it, returning TRUE. If the integer does not exist in the set, the function returns FALSE.
• GetRandom(): This function takes no parameters. It returns an integer chosen at random from the set.

Note: Your implementation should aim to have a running time of $O(1)$ (on average) for each operation.

Constraints:

• $-2^{31} \leq$ data $\leq 2^{31}$
• No more than $2 \times 10^5$ calls will be made to the Insert(), Delete() and GetRandom() functions.
• There will be at least one element in the data structure when the GetRandom() function is called.

Examples