Solution (leetcode-in-java 1.19 API)

java.lang.Object
- g0301_0400.s0398_random_pick_index.Solution

```
public class Solution
extends Object
```
398 - Random Pick Index.
Medium

Given an integer array nums with possible duplicates , randomly output the index of a given target number. You can assume that the given target number must exist in the array.

Implement the Solution class:
- Solution(int[] nums) Initializes the object with the array nums.
- int pick(int target) Picks a random index i from nums where nums[i] == target. If there are multiple valid i’s, then each index should have an equal probability of returning.
Example 1:

Input
```
 ["Solution", "pick", "pick", "pick"] 
 [[[1, 2, 3, 3, 3]], [3], [1], [3]]
```
Output: [null, 4, 0, 2]

Explanation:
```
 Solution solution = new Solution([1, 2, 3, 3, 3]); 
 solution.pick(3); // It should return either index 2, 3, or 4 randomly. Each index should have equal probability of returning. 
 solution.pick(1); // It should return 0. Since in the array only nums[0] is equal to 1. 
 solution.pick(3); // It should return either index 2, 3, or 4 randomly. Each index should have equal probability of returning.
```
Constraints:
- 1 <= nums.length <= 2 * 10⁴
- -2³¹ <= nums[i] <= 2³¹ - 1
- target is an integer from nums.
- At most 10⁴ calls will be made to pick.

- Constructor Summary
  
  Constructors
  Constructor Description
  
  Solution(int[] nums)
- Method Summary
  
  All Methods Instance Methods Concrete Methods
  Modifier and Type Method Description
  
  int pick(int target)
  - Methods inherited from class java.lang.Object
    clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail
- Solution
```
public Solution(int[] nums)
```

Method Detail
- pick
```
public int pick(int target)
```