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 Summary

Constructors

Constructor and Description
Solution(int[] nums)

Method Summary

Modifier and Type	Method and 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)