Package g0301_0400.s0398_random_pick_index

Class Solution

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 Details

    • Solution

      public Solution(int[] nums)

  • Method Details

    • pick

      public int pick(int target)