Solution: Random Pick with Weight

Statement

You’re given an array of positive integers, weights, where weights[i] is the weight of the $i^{th}$ index.

Write a function, Pick Index(), which performs weighted random selection to return an index from the weights array. The larger the value of weights[i], the heavier the weight is, and the higher the chances of its index being picked.

Suppose that the array consists of the weights $[12, 84, 35]$. In this case, the probabilities of picking the indexes will be as follows:

• Index 0: $12/(12 + 84 + 35) = 9.2\%$

• Index 1: $84/(12 + 84 + 35) = 64.1\%$ ...