[Leetcode] Random Pick with Weight randomly based on weights

Given an array of w positive integers, where w[i] describes the weight of index i , write a function pickIndex which r Andomly picks an index in proportion to its weight.

Note:

1. 1 <= w.length <= 10000
2. 1 <= w[i] <= 10^5
3. pickIndex'll is called at the most times 10000 .

Example 1:

["Solution", "Pickindex"]  [null,0]

Example 2:

["Solution", "Pickindex", "Pickindex", "Pickindex", "Pickindex", "Pickindex"]  [null,0,1,1,1,0]

Explanation of Input Syntax:

The input is a lists:the subroutines called and their arguments. Solution' s constructor has one argument, the array w . Has pickIndex no arguments. Arguments is always wrapped with a list, even if there aren ' t.

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[Leetcode] Random Pick with Weight randomly based on weights