Package g0501_0600.s0528_random_pick_with_weight

Class Solution

java.lang.Object
g0501_0600.s0528_random_pick_with_weight.Solution
public class Solution extends Object
528 - Random Pick with Weight\. Medium You are given a **0-indexed** array of positive integers `w` where `w[i]` describes the **weight** of the ith index. You need to implement the function `pickIndex()`, which **randomly** picks an index in the range `[0, w.length - 1]` ( **inclusive** ) and returns it. The **probability** of picking an index `i` is `w[i] / sum(w)`. * For example, if `w = [1, 3]`, the probability of picking index `0` is `1 / (1 + 3) = 0.25` (i.e., `25%`), and the probability of picking index `1` is `3 / (1 + 3) = 0.75` (i.e., `75%`). **Example 1:** **Input** ["Solution","pickIndex"] [[[1]],[]] **Output:** [null,0] **Explanation:** Solution solution = new Solution([1]); solution.pickIndex(); // return 0. The only option is to return 0 since there is only one element in w. **Example 2:** **Input** ["Solution","pickIndex","pickIndex","pickIndex","pickIndex","pickIndex"] [[[1,3]],[],[],[],[],[]] **Output:** [null,1,1,1,1,0] **Explanation:** Solution solution = new Solution([1, 3]); solution.pickIndex(); // return 1. It is returning the second element (index = 1) that has a probability of 3/4. solution.pickIndex(); // return 1 solution.pickIndex(); // return 1 solution.pickIndex(); // return 1 solution.pickIndex(); // return 0. It is returning the first element (index = 0) that has a probability of 1/4. Since this is a randomization problem, multiple answers are allowed. All of the following outputs can be considered correct: [null,1,1,1,1,0] [null,1,1,1,1,1] [null,1,1,1,0,0] [null,1,1,1,0,1] [null,1,0,1,0,0] ...... and so on. **Constraints:** * 1 <= w.length <= 104 * 1 <= w[i] <= 105 * `pickIndex` will be called at most 104 times.

  • Constructor Details

    • Solution

      public Solution(int[] w)

  • Method Details

    • pickIndex

      public int pickIndex()